I believe it’s more PCI-E 3.0 x 2 (lanes) rather than the old school PCI-E 2.0. It’s running off the chipset, rather than directly to the CPU, and will need to share resources. From my understanding, Ryzen (all of them) have 24 lanes to share. So, 16 are made available for GPU, 4 for the m.2 that’ll run directly to the CPU and 4 for the chipset. So all secondary m.2 drives will have to share resources in the same way. It’s why it has to turn off the PCI-E slot if the drive slot is populated.