Quote from that interview:
“…it is unhappily true that we have these consoles here running at sixty frames per second, and we could have these massively more powerful PC systems that struggle sometimes to hold the same framerate because of unnecessary overheads. If we were programming that hardware directly on the metal the same way we do consoles, it would be significantly more powerful.”

It's not the fault of the consoles that Rage doesn't look tremendously better on PC.
The overhead he's talking about has nothing to do with the multiplatform concept of Rage but with the PCs geriartric architecture of using drivers to communicate with the hardware.
Rage is not "a console game ported badly to pc".