They have mentioned a few times (though nothing with specific numbers) that games have a lot of data redundancy to work around poor HDD seek times.
Given the drive speed it might be nice if games could auto-archive into a USB-attached device. The XBox requires custom SSD hardware for expansion (those weird non-USB drives?) and the PS5 will require swapping out the SSD entirely to expand usable space.
... but sequentially copying a compressed archive to a fast USB3.1 device might not be so bad for games not currently in use.
I don't think it's been confirmed whether they'll be enforcing a whitelist, or merely publishing a list of drives that have been verified to be compatible. The latter seems more likely to me, simply due to the sheer volume of SSD models that will meet the technical requirements. (Especially where we'll see a dozen or more brands selling the same hardware with a different label.)
Given the drive speed it might be nice if games could auto-archive into a USB-attached device. The XBox requires custom SSD hardware for expansion (those weird non-USB drives?) and the PS5 will require swapping out the SSD entirely to expand usable space.
... but sequentially copying a compressed archive to a fast USB3.1 device might not be so bad for games not currently in use.