The question of required specs for PS5 to use off the shelf SSDs does remind me of Sony's custom I/O controller (e.g. the 6 levels of prioritization Cerny mentions). Seems like that could be attractive as open spec, let's call it "Play I/O", that SSD makers could utilize and market as performance standard games might target. Beyond a certain point massively higher speeds don't seem that imporant to consumers, and higher tier I/O system seems more efficient way to deliver performance. In other words SSD makers could still differentiate themselves as "more premium" using "smarter" I/O control rather than more expensive underlying flash chips etc. They could still offer higher speeds than PS5, with faster underlying chips and same I/O controller architecture, consolidating on standard for latter still being useful. Sony would benefit by having it standardized because every performance dependent game would be optimized for PS5's architecture, ensuring it's well supported.
Anyways, in absense of that,
Yeah it looks like you'll just need an off the shelf EDIT: PCIe4 NVME SSD with speeds slightly above Sony's to compensate simpler controller.