That "reverse" trick works because it forces a downshift to1st. gear, not reverse, because there's a safety circuit in the transmission valve body that prevents actually engaging reverse until the car slows down to below 10 MPH or so. It has the same effect as locking up the rear brakes only while the front wheels keep rolling. Try that on a front wheel drive car and you'll provoke a corkscrew spin that's totally uncontrollable or a rollover as the rear end whips around in a fraction of a second.
