I think that's normal. If you connect a keyboard to a USB3 port, all you need is 12Mbps. All my USB receiver for keyboard and mouse and Aura LED, also show up as 12Mbps. If I connect USB3 thumb drive, it shows up as 5Gbps.Thank you, but I tried your attachment 2 on High Sierra and use my config.plist it didn't work at all, all the ports are still detected as usb2.
I think I'll get a cheap 2nd hand AMD card and install Catalina and see..