RS-485 is just a physically extended RS-232 communication with differential signaling.

Exactly and the differential signaling means two wires with opposite signal value where at the receiver both signals are differentiated such that any noise on the signal will influence both wires and due to the differentiation the induced noise will be eliminated.

And therefore this can in theory never be realised wirelessly where a too large noise will eliminate the reception of the original signal

Even to be more precise, when you divert from using two differential wires for transmission it is per definition no longer RS-485 , therefore the problem should be redefined.

What a beautifull trick question for an exam.