That would make sense, as I have noticed the same thing in Québec City and was rather confused about it. For me, returning the card first makes so much sense that I wondered how people could implement this differently. A lot of people will grab the cash, their brains will subconsciously tell them "I have what I came here for" and they will leave - without their card.

I see really only one potential advantage for doing it this way: you can provide other transactions after dispensing cash. So you could get some cash and then afterwards check your balance, for example, without having to re-enter card and PIN code. With the "international model", cash withdrawals are always the last transaction in the series as the card will always be withdrawn as part of the transaction. Nevertheless, I would judge this "convenience factor" as far less important as the protection against forgotten cards.

But maybe someone here works in the Canadian banking industry and has some clues? Maybe the recording of the withdrawal transactions works differently and the ATM needs the card for a short period after the money has been dispensed? I don't know...