I think what he is talking about ( I have experienced this too ) is the effect of how much you lean over... visualize how far your butt sticks out when you bend over... by trying to bend over with your heels against a wall... you can't... (I can't) so when you rump moves back the balance goes more over your feet, you may lean over, but less forward... hence moving your seat back to essentially move your feet forward relatively... this allows less pressure on your hands ( yes pros?)