Current policy (on GNE at least) seems to be that the driver waits for passengers to reach a safe location before they set off (and passengers are recommended to remain seated until the bus stops.
This can extend boarding times, especially if the passenger is 'infirm', and, to have to wait whilst said passenger climbs the stairs and reaches a seat (which many drivers do do - at least in Tynedale) can delay the bus even longer.
I only climb the stairs if I am travelling a 'long way' (rather than just between Hexham and Corbridge) and I like to sit in the front seats so that I can enjoy the view.
RE: Go North East: Latest News & Discussion - May 2015