The false grip on the rings serves two common purposes: one, it shortens the lever of the arms slightly; and two, it prepares for the transition of the athlete from under to over the rings, as we see in the muscle-up. Place the hands in the position in which you would want them for a ring dip and then lower the arms to find the basic false grip position—it will not be comfortable and it will likely take some time to develop the strength to maintain it.