I suspect what the
convertor does is take the frame, and send it out the USB in whatever format it
needs to be data intact.
It sends highly processed(/extracted) data to a device driver running on
the PC. Just like an ethernet adapter on a PC-card would. If it were in
any sense still "ethernet" data, there would have to be an "ethernet
card" inside the PC on the 'inside end' of the USB. And there isn't.