This reminds me of a tour I did several cruises ago. There was an elderly couple sat on the fron seats. At every stop the gentleman stood up, blocking the exit, whilst his wife slowly shuffled off the seat, and was assisted down the steps. The whole coach load of passengers was held up. There was another door near the rear but the driver wouldn't open it as it was "only for emergencies". I think we must of lost at least five mins at every stop. Quite a chunk of a 15 min photo stop.
I don't know how the wife felt but I would have been embarrassed to hold everyone up.
I have never understood why wheelchair users should have priority either. Due consideration and understanding to their difficulties, yes. But priority I never understood.