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.