I have to agree that the airport story seems extremely fishy. I fly a lot out of YUL and have never had exit passport controls, either to the US or intl (for that, there is an automated turnstile scanner now). Your theory Acajack that he's referring to the Catsa dude scanning your bp and eyeballing your passport at ingress is pretty much the only explanation, but those clowns are hard to mistake for customs officials, and they do not wear anything resembling a Canadian border official uniform with a prominent maple leaf on it.
This didn't happen.
Anecdotally, my experience with YUL Catsa staff in particular is that they struggle with both French and English
As for the rest of the airport staff, never had issues getting served in French, as you noted.