On my first, only, and LAST experience with PAL, the passengers carrying on to Toronto, didn't even get off the plane. Now I didn't have landing procedures to do BUT, I didn't clear customs until I disembarked in Toronto. So if it's the same plane and you don't disembark, you won't "land" until Toronto. This is from "personal" experience.
All the other major airlines (not transiting through the U.S.), have stopovers outside of Canada, making it a sure thing . . . that you will "land", once you land in Toronto. Unless PAL is absolutely the cheapest available, I don't recommend them. They're very annoying to deal with.