Swing plane

It is easy to understand the reasons for the difference in ball position when you consider the swing plane. With a splash shot you are looking to create a more upright swing plane so the clubhead can dig into the sand two inches behind the ball, but then slide under the ball popping it up and out. Splitting the weight evenly assists the creation of the correct plane. When hitting a flop shot a flatter swing plane is required to ensure a very shallow angle of attack.