I’d be inclined to think that either arrangement could still result in the same basic flow of staff.
Whether it was a balcony pay hatch or an internal desk/counter, you could still have a line forming up the steps on one side, with staff waiting their turn, and then exiting via the steps on the opposite side once they were finished. That kind of one-way circulation would make sense in either case and would help avoid blocking the queue.
Just speculation my part as I haven't seen evidence of either.