the femur length theory seems to be bogus. If you look up kotg's 'seated good morning', that is the motion that is crucial. It takes really good groin flexibility (and probably flexibility in other pelvic muscles) to be able to get a straight torso really close to the thighs. KOTG has this flexibility. Most people do not and thus most people can't do a foot-on-ground squat (unless really hunching the torso forward to avoid falling backward).
