They promise non-existent loading times, which no PC can achieve no matter the configuration.
The SSD is apparently a Samsung 6 series PCIE 4 Nvme Drive. That's plenty fast.
The reason the PC can't do better than it has now is the architecture for the flow of data.
The PS5 is aiming to do things differently to a PC. In addition to the PCIE 4 SSD, it's also uses Sony's 3D ReRAM memory.
Here is my rough understanding of the data flow
PC Load and Play Game: Call SSD -> Process and transfer data into RAM -> Boot game -> While in game, continue this process for loading new levels and assets.
PS5/Next Gen Console: Call SSD -> Process and transfer data into ReRAM -> Transfer data into RAM when called -> Boot game -> While in game, continue to process data into instant ReRAM -> When game asset is called, it's instantly transferred into RAM.
So when a PS5 boots a game, the only loading screen you see is while the game boots the first time, after that there is no loading because the data the game needs is sitting in super fast ReRAM and waiting to send it. This effectively makes the whole process several times faster than an SSD in your desktop PC.
As per the below image, you can see the ReRAM falls closer to your DRAM in terms of access time and is much faster than existing NAND SSD technology.