That's really stupid.

After pretty much every YYC do, I would book the Sunday evening YYC-SFO non-stop, and I would inevitably wake up late enough that I couldn't get to YYC until about noon. At that point, the soonest I could get home to SFO was consistently YYC-YEG-SFO.

I can somewhat appreciate not letting you change your 0900 non-stop to a 0900 connecting itinerary, but if I can't change a 1700-1900 non-stop to a 1200-1500 connecting itinerary, it means I get home 4 hours later than possible, and have to sit at the airport for 5 hours.

Your case is also a reasonable example from the passenger side.

I guess there's no point buying a fare with free SDC if you're flying a route that only has one daily flight.