Well, I looked into the sales # of 1989 and 1990 on wiki and looks to be somewhat different from yours. You can check out on the wiki as they also have sources sited.
According to Wikipedia,
1989 alone, Genesis sold 500k units in U.S. 1990, 1M units.
TurboGrafx 16 sold 300k in 1989, and 450k in 1990.
I don't see what you're saying, but even if it is as you say (I was able to find another version of the article your referencing with the same numbers) the context is out of wack, and the numbers aren't attributed to Sega, it's just said.
Sega gave out the 1.2 million number in late April of 1991. Sales momentum would have had to collapse if they sold 1 million consoles by late 1990. 500k also seems too large, maybe shipped but sold? I can't see it. The article referenced I can find is mainly talking about Sega's hopes for the Game Gear and randomly just brings up 1 million Genesis consoles out of nowhere.
Paducah News Jan 11th 1991
Kalinske gave a range of 600-650k sold in 1990.
Now, last time Sega and NEC gave ranges they were shipped figures, which is why i didn't include that in the OP, but in this case even if we were to take these numbers literally, which is bad because of contradictions before and after this, even if we took 600k they still wouldn't have been at 1 million units sold combined 1990 and 1991, and that's going off Kalinske giving this skew. He says 61% up from 1989.
That means using his numbers 1989 sold either 366k or 396k depending on which part of the rage you use. In either case using these likely shipped numbers and using either number adding to 600k, adding both years together still would not give you 1 million consoles and that's with PR inflation.
Only if you use the higher end would you just get over the line but of Sega sold 1 million they wouldn't have forecasted passing it in 1991 and they would have announced it. Even Kalinskes own interview posted in the wikipedia article shows that Sega of Japans goal for the console was 1 million nd when they did pass 1 million Sega was going to the press starting with a hard to find 1.1 million and then the 1.2 million that was circulated more I linked in the OP. If they had 1 million why wouldn't have Kalinske just mentioned it right then in the article instead of doing another shipment range that was done the last time Sega (and NEC) gave a range instead of a solid number?
Sega themselves announce 1.2 million units in late April (1.1 million before that) that's almost May, 5 months into the year, CES was jan 10th 1991 when the Sonic anticipation (and other games shown with it by proxy) there's a clear trend of genesis sales picking up after that CES.
Even when Sonic was shown again before release it still got gawking attention
The hype wasn't fake s the haters say, or overblown, it was real.
This was in June 4th 1991, less than two months later from the 1.2 million announcement landing on the same month as Sonics launch and second demonstration and there's a 200k sales jump. Over 2 million by late Sept, that's a 600k sales jump less than 3 months. A month after that, 2.3 million which as shown in the OP, is another 300k jump.
It's very clear that Sonic since it's first showing at January CES in 1991 was the source of the increasing interest in Genesis sales, and that exploded once the game was actually released. Going off the trends, it's also clear that there's no way that 1 million sales, including Sega's silence on the matter, happened in 1990. The best hypothesis is they passed 1 million at the earliest in February 1991, though i think that may be a bit too early i can see that possibility. Followed by 200k sales between February and late April, that is plausible. But before that starts to get unbelievable.
Maybe TG16 and games were more readily available in bigger cities
That was their game plan yes, they went with a trickle down strategy, but unlike Japans urban set-up which could be compared to a rich-poor dystopian movie, in the US the trickle down strategy doesn't actually work. Granted, NEC did improve just not enough as they still focused a lot more on major cities instead of going for having major centers as a priority, but having fair distribution throughout in between, that should have been their strategy.
However, the first strategy worked so well in Japan, and NEC basically owned the country in multiple electronic categories so badly, that they likely thought given that they were somewhat a big name in tech overseas, the same strategy would work. But that's more NEC not bothering to do some research on the market before hand which they could have done easily since they had the cash and the resources, they just decided not too.
Of course, they did ok as the thread indicated early on, and honestly, even if they were to be a bit smarter without they distributed systems to retailers I don't see anyway it would improve their situation. Without a new hit that could do double Bonks numbers, which did well initially and was the best selling 16-bit game for a time, with no game at least half as appealing as Sonic to drag consumers to its ecosystem I just don't see any way out for NEC. Sonic was already hurting them when it was announced, after it came out NEC's sales basically froze, and when you add in additional salt with the SNES which almost sold two years worth of sales of either consoles in a few months, NEC loses that window of opportunity they had.
CD never took off because it entered too expensive, and NEC slowly dropped the price and then stopped, the TurboDUO was not priced to rectify that and Sega came out with a cheaper CD expansion which NEC had to price cut to match that ended up selling both forms of Turbo CD 5:1 and it still sold to slowly and ended up being a dud in the long term. CD was NEC's backup plan if they couldn't get another major hit.
I'm well aware of the Japanese library, and there was nothing in NEC's arsenal to pick up sales even at half Sonics level unless it was on CD., which was $400 on introduction and without much software ready.
Hucard games once CD started gaining ground in japan basically hit the dirt. Some modest sellers showed up but the last leg of the PC Engines life was dominated by the CD expansion and the Turbo Duo console which Japan had two versions of and almost marketed them as new consoles even though they weren't. Without CD working in US I think NEC was always screwed when Sonic came out and made Sega a genuine competitor, Super Nintendo came from the company that blocked out the competition (literally) and dominated the country nearly unopposed, and while you could make that argument for Japan, over there NEC was the only viable competitor and had a year head start and got the CD out early and had time to convince Japanese consumers to adopt it. In the US, Sega and NEC were out close to each other, while there was a market slump, in a much more cost conscious country where having little software ready for your $400 device which requires consumers to buy a console to even work, is usually a death sentence. There's also not much time to get things in order ether, with both NEC and Segas consoles picking up after slow burning launch months, NEC would have had to have a hit or hits to stay ahead and to counter the eventual Super SNES release, they didn't.
What NEC likely should have did that may have worked, at least for them to remain a player and maybe that Supergrafx console may have ended up not being a 6 game flop, or maybe the PCFX would have sold more than 50,000 units, is that they should not have tried to position the (to the US) new Turbografx and the Turbo CD at the same time.
They should have done it like Sega (but better) where they build the brand and games up with the base console first, and then launch the CD either at the same time or just before the Mega CD Sega put out in 1992, that way more games are ready and the price for the player would be lower. Also given this is NEC in the 90's, they could undercut Sega by $50 too.
That's the only way i see this working, otherwise, without CD NEC only system seller was Bonk, and they screwed up the sequels appeal and nothing else they had that could be released before 1992 would move anything in the US, and the games that could would release too late.
It sucks, but their position was always screwed without the CD. Worked in Japan, for a bit but even that ran into the "lack of appealing Hit game" problem and after the Super Nintendo had been out there for awhile NEC fell to pieces even though they were number two.