You’re not loading 20 million triangles 30fps from storage.
Majority of this is happening from memory. You’re only loading in new data coming in and old data out. There is still a buffer period. PS5 can have at most a theoretical 50% shorter buffer length than XSX (very unlikely). Doesn’t mean buffer is gone.
the only way SSD is the bottleneck on pS5 is to require the hard drive to be running a full 5.5 GB/S every single second without rest. Be reasonable. That’s not virtual texture streaming at all.
there is a large buffer wrt to the performance of the hard drive or we would be hitching everywhere.
It depends on the games.
I think the challenge is when the character keeps moving, teleporting, and changing direction/view points. It's usually the edge cases that break/stall/pop-in things. It depends on how much freedom they need/want.
The other aspect is if it's user-generated assets, they may not be as optimized as developer-generated ones.
Plus what else the system is doing at the same time causing resource and bandwidth contention. And how complex and open the world is.