Slashing to 12% on game sales and MTX would only ever make sense if they were having trouble bringing devs over to the platform. That's a really big cut, you can do the math. Savings wouldn't be passed on to the costumer either, so we get nothing from this.
It being studied as a way to convince some developers to give up streaming rights is a sign that they are having trouble getting those streaming rights to use on Xcloud and/or are having to pay over the odds for those streaming rights.
Geforce Now biggest battle is getting devs/publishers to allow their games to be streamed on geforce now, even though Nvidia isn't selling games, nor access to those games. Their model relies on the end user buying games from stores like Steam, Epic and GOG, and even still you have publishers saying "Pay me, fuck you". So you can imagine how expensive it gets when you want a game on a subscription service and exclusive streaming rights.
Also the more streaming services there are, the more leverage publishers/devs will have to negotiate better deals.