XPS 8940, 990 PRO PCIe 4.0 NVMe M.2 SSD 1TB, slow performance

The achieved speed is on par with PCIe Gen 3, up to 32 Gbps the XPS 8940 can support.  PCIe Gen 4 or Gen 5 SSD will be backward compatible and running at a PCIe Gen 3 speed.

Provided you set this drive up properly, you won't see a faster drive on the 8940 (using the M.2 interface).

That is a fact.

Drive throughput for most people, is not a big deal.