You can't *toggle* USBNet (i.e., run ;un) with the cable plugged in, but that doesn't mean you're forbidden from plugging it back in right after
.
The KUAL toggle button is much more explicit about that (and it will in fact abort the toggle to avoid mishaps if it detects that the device is plugged in).
Other than that, what @j.p.s said: the README is entirely concerned about USB.