Why is my new Gen 4 SSD running at such slow speeds?

I recently picked up an ADATA Premium M.2 Gen 4 SSD for my PS5 for a good price—only CAD 93 (about USD 68) and it's showing 99% health. The SSD works, and I've noticed that some games, like Street Fighter 6, load significantly faster. However, the speed of the SSD seems to only be about 25% of what's advertised. I've checked the health using CrystalDiskInfo and HD Tune without any errors. I'm using an Aorus X470 Ultra Gaming motherboard, and it looks like my setup includes an M.2 socket that supports PCIe 2.0. I was wondering if this might be why I'm not getting the full speed. Can anyone shed some light on what generation my M.2 B socket is and how to get better performance?