Just ran disk mark against my two drives. Both are hitting their rated speeds at PCIe 3.0 x4. 1TB Samsung PM9A1 (stock main) and 2TB Pioneer APS-SE20Q-2T (added secondary). So it doesn't
SAMSUNG PCIE 4.0 SSD PM9A1 6400MB/S - YouTube
Amazon.com: Samsung SSD 1TB PM9A1 NVMe PCIe 3.0 Gen3 x4 MZVL21T0HCLR 00BD1 KG5N3 0KG5N3 Solid State Drive for Dell Alienware HP Lenovo Laptop Desktop : Electronics
Amazon.com: Samsung SSD 1TB PM9A1 NVMe PCIe 3.0 Gen3 x4 MZVL21T0HCLR 00BD1 KG5N3 0KG5N3 Solid State Drive for Dell Alienware HP Lenovo Laptop Desktop : Electronics