This, This and so much this. I love when I see people try to hype up this like its the 2nd coming of SSD tech. I guess all Sony's other proprietary tech was so much better than their counterpart UMD, Sony memory sticks, etc. This is just a way Sony can charge you god only knows how much for an SSD drive so you can't just go buy a cheaper SSD drive for your PS5. Well at least until someone makes an adapter like with the Vita memory cards.
The problem is no one is talking is a second coming of SSD tech, i also need to remind you that Sony has their own memory tech patent which is Re -Dram it is better then stack memory tech the current SSD's has, although it's still more expenses then normal DRAM .
Not all proprietary will be expensives, nor proprietary means you all need to pay for. Also my suggestion it's for expandable storage that connected directly through some proprietary fast connector instead directly open to the PCi- bus on PC/ PS5 Motherboard. PS4 are easier because they are using SATA , a faster SSDs for PS5 required a NVme that directly connected to the Mobo. That will be difficult to non PC especially casual. That's why they came with this solution.