hi! that's exactly the reason they gave me too. but it seems a little disingenuous to me: just because the train does not stop there, doesn't mean the fare cannot be calculated, it just means they do not calculate it. If the ticket on the IR and the S-bahn is the same between Baden and Zurich, i don't see why it cannot be calculated.

This restriction on combining the Abo and normal fare ticket on the IR seems like a grey area to me and the SBB would rather burden the traveller with either using the Abo and a longer ride, or not using the Abo and spending more.