Well we don't know whether the data given for the PS5 SSD is sequential or random, sustained or burst. We also do not have the latency or the IOPS for the PS5's SSD. They haven't confirmed that information and I honestly don't expect Sony to, because they do not really need to. PS5 is going to sell millions of consoles regardless.Those peak speeds are only for sequental reads. Random reads which are more inline to your actual usage don't hit those speed...
Here's a comparison random 4k read (wd blue sn550 chosen to represent XboxX storage, based on sequential reading speeds):
Here is that same benchmark on the 980 pro
Notice that the WD blue peaks at 390,000 iops at 800 miliseconds while the 980 hits 390,000 iops at about 100 miliseconds and tops out at about 550,000 iops at 250 miliseconds.
Personally, I don't expect this to have any impact whatsoever on graphics, but the quality of life of almost instant storage is just magical.
My major point though, is that the streaming pool size for an advertisement of the capability of next-gen is not an unreachable goal for most modern SSDs, which makes sense since the Unreal Engine is targeting every device. If a current gen game requires a large 10 GB streaming pool for memory reducing down to a 768 MB pool is a 1:13 ratio or a 13x increase in bandwidth. Far cry from the 100x increase in data transfer speeds.
The raw speed will make a difference in asset loading, but it's impact and the true next-generation leap will not be realized until games have enough asset data to fully saturate that SSD speed.