Unfortunately the only requirement is that priority dictates who gets on the aircraft, not what seat they get.

They can clear out of order if they know everybody is getting on. It sounds like your experience is different, but the only time I've seen it personally is if they are trying to keep a party together (usually a family), otherwise it seems they usually give out EMS seats in order.

If you commute out of that city regularly I wouldn't pursue it because 1) there is no written policy, and 2) I wouldn't want to be "that guy" in the agent's eyes in my home city.