Why Is My M.2 Gen 4 SSD So Slow?

I recently bought an ADATA Premium M.2 Gen 4 SSD for my PS5, and it was a great deal at $93 CAD ($68 USD). While it's working fine and some games like SF6 load faster, I've noticed that the speed is only about 25% of what I expected. I checked the health of the SSD using CrystalDiskInfo and HD Tune, and everything seems fine. My motherboard is an Aorus X470 Ultra Gaming, and according to the specs, there are two M.2 connectors: one that supports PCIe 3.0 and another that supports PCIe 2.0. I think I'm using the PCIe 2.0 slot, which might explain the speed issues, but I can't find clear info on the M2B socket's generation. Can anyone clarify this for me?