Speedy boarders if transferred by bus are told to stand by a particular door. Only that door opens. Theoretically allowing only the speedy boarders to get off first.
But it always amazes me why everyone seems to head for the front steps of the aircraft.
We always head for the back steps, found our chosen seat at the rear, hand luggage stowed, and sat down watching passengers at the front holding up others getting on.
Normally there are steps at the rear on arrival, so we are getting off at the same time as people who think sitting at the front will get off sooner.