Clearly decided by someone that is only familiar with travel between YYZ-YUL and has never set foot inside a smaller airport except for YTZ. I'm sure the longer checkin deadline makes sense for most of the
top 10 airports in Canada, but for the rest? REALLY? For smaller airports I have the most experience with YYG where you can show up 30 minutes before the flight and still have too much time on your hands. I would expect that most of the smaller airport in Canada are similar.
Incidentally, according to Wikipedia, YYT is the #9 airport in Canada