This makes complete sense to me.
I have another anecdote from reddit of a Canadian PR/ US citizen flying back from the states to their home in Canada. So everytime this person flew, they used their US passport and didn't bother showing the Canadian PR card at check-in. Always waived through no...
I haven't read everyone's input on this thread yet, and there seems to be a really good, in-depth discussion going on. I skimmed and have some thoughts on some of the points and anecdotes raised, but for now, I just want to give an update of what I learned calling some airlines and CBSA.
1. Air...
This is precisely right. However, the airlines base their decisions on who to board on govt regulations. So far unable to determine what these regulations are and which is the body that governs them.