The fact that he went backwards instead of forward with leg pressure tells me he has no clue what leg pressure means. I think it was CA I was recently reading about this from. But he explained that when 'squeezed' with leg pressure, forward is the last place a horse will look for it. What he did (and what I would do if I didn't have the magic that is Clicker Training :P) is teach the horse on the ground - that when you apply pressure to one rein that it isn't to just turn their nose to their side, but to also disengage their hip.
I also agree some quality ground driving will help teach a horse 'forward' - will also help with verbal commands that can translate to mounted work.