As I said, the SSD isn't connected to this card, but instead to the PC's motherboard separatedly, which doesn't have the same I/O (reading and decompressing by hardware the SSD data, allocating it in memory, memory management) like a PS5.
Reason being an SSD is too big and heavy to put it in a card, and isn't needed to replicate the exact SSD behavior for what a devkit is used (which isn't the same than a retail console or testkit). So for them is better to keep it separatedly, something it also reduces costs for the card.
It also provides more flexibility, like to have different SSD sizes or multiple SSDs if desired. Because devkits often include extra RAM and storage, because they aren't made to run retail versions of the game, but instead early, unoptimized versions of the games during early stages of development, where in addition to the normal game code, on top there are many debug related stuff plus metrics and telemetry stuff to track the behavior or performance of several other things. Meaning, the performance of the game isn't the same than in a retail console, and devs don't care because in early stages of development this is not the important thing where they are focused at.
Once a game is on its final stages of development it's tested instead in testkits, which are way closer to retail consoles