I would think a question clarifying whether she does incalls wouldn't be out of line. Note this other ad she posted just a little bit earlier the same day in which she says she does incall/outcall.

http://minneapolis.backpage.com/FemaleEscorts/m-a-ke-my-ki-tty-kat-pur-r-18/5429401

This ad says outcalls only and below that, it says incalls only.  Am I an idiot if I ask for incall?  Am I an idiot if I ask for outcall?  Or am I an idiot if I call at all?

I don't see the word only in this one.

The questions were not so serious as an amusing tale of mutual exclusivity.

yes