PCI-SIG specs are continuously updated. See pcisig.com/specifications/pciex … fications/
Optional USB 3 SuperSpeed support was recently added to the Mini Card spec:
pcisig.com/sites/default/files/ … _Final.pdf
Note that this document leaves it up to the platform to select USB 3 or PCIe interface. Older platforms will of course not know anything about this, so they will use those pins for PCIe if connected. And you end up with a rather confused PCIe system.
Tape is the correct solution. I did the same to use an MC7455 in my oldish laptop. But you won’t get USB 3 support that way, of course. Note that you probably only need to cover the USB3 TX/RX pairs, and that it doesn’t matter if you cover the ground pins between them. So you can just put a single piece of tape over pins 23, 25, 27, 29, 31, and 33.
I believe the reasoning behind this design choice is that the Mini Card form factor modules are meant for new embedded designs, where the Mini Card slot is wired up specifically for those modules. The m.2 modules are more appropriate for the laptop market.