I also noticed USB and Dummy, they should both work.
But I couldn't make it work yet. The Linux machine pings to the tablet, but not the other way around.
No Internet has been shared yet... not an Mac either.

I think Windows should see it as an rndis device, yes.

If tonight my GF give me 30mins to test this stuff I could test it on the Mac and on Windows (inside Parallels).