They were on the tarmac. It continues and says that “the Carrier must allow the passengers to deplane....”
Let me read the Air Canada one. The Air Canada one says that it “will not permit an aircraft to remain on the tarmac at a Canadian or US airport for more than four (4) hours”.
These are the tariffs that are published by those two particular airlines. That's their decision to do it. If, for example, after we put out a three-hour tarmac delay, one of those airlines decides it still wants to keep 90 minutes at the gate, they're perfectly free to do it, but if it's out on the tarmac, our three hours will actually be better than the four hours most people are required to wait. Also, within that three hours, there will be a requirement to provide refreshments, information, air conditioning, and bathroom services—all of those things—during that period of time.