Jim believes that when you shoot using the sights, your conscious mind is occupied with the sight picture. He further believes that the subconscious mind works faster than the conscious mind. While you have been consciously training with a formal sight picture, your subconscious mind has picked up on a bunch of subtleties about how the gun is aimed. In particular, the subconscious mind knows what the silhouette of the gun looks like if it is aligned with the target. Thus, the gun is visually aimed solely by its shape.
Many students actually shoot better with the sights taped.
His theory on this is that since they cannot see a traditional sight picture, they don't jerk the trigger when they think they've got a perfect one. The purpose of the silhouette point is to get the gun aligned and fired more quickly, by relying on your subconscious mind. The method is independent of the position in which you grasp the gun. Jim also teaches two variations on a technique where the gun remains below the line of sight. The trick here is to keep the gun parallel to the ground as you lower the gun from your sighting plane to the level at which you want to strike the target.