I might be wrong but over the course of about 6 years climbing at the Rockface I cannot remember anyone being in charge that did not have good knowledge of climbing. I would also add that most, if not all have experience relating to indoor and outdoor climbing. They do a bloody good job, think of the responsibility they have when supervising in a gym which offers climbing access to the general public.
I was always taught to dress the knot properly and have a little length left after the figure of 8, say 15cm. Too little is not good, too much is a nuisance and a liability so needs tidying up.
cheers