Not an area I'm familiar with, but do the chips really handle up in the gigabit IO? I thought they just handle connection setup. I had thought the gigabytes were not processed at all by the chips. They just flow through the wires.
"Cable" is loosely defined, but a cable with usb-c on one end and anything else (eg HDMI) on the other has to do some processing of the signal in order to do that.