The crew would normally intervene if they were NEXT to the Exit - but often if they are in the middle or aisle seats of an EXIT ROW then they'd be allowed to stay there, so long as the person at the Exit was clearly fit and able.

By the time the AGP pax had got to the Seats both the Check in agents and the Gate Staff have confirmed they are fit and able to it there, the cabin crew would be a third line of defence.