For a body drop to add any significant energy to a technique, the body must have increased acceleration. Since no other acceleration may be added to a sine wave body drop, the only acceleration is that added by gravity to the free-falling body. Since the distance of the fall is only a couple of inches, the acceleration is negligible. With the hip snap, body musculature adds significant acceleration and energy to a technique.
The sine wave motion telegraphs movement. For example, suppose you are in a fighting stance with your guard up, and the opponent watching your leading fist. If you execute a jab, what visual cues do you give the opponent that might tip him or her off to your attack? For a snapper, the opponent may notice that the fist appears to be getting larger. At some point, the brain computes this to mean that the fist is getting closer, but it is probably too late to react. For a waver, the fist rises and then appears to get larger. The initial rise telegraphs the jab, giving the opponent a split second more time to react.
Professional boxers make their living from punching opponents. If sine waving was more effective, they would use it. Instead, they use hip snap. They do bob and weave, but this is an avoidance movement not an attack movement. Baseball hitters, golfers, tennis players, and disk golfers do not rise and then drop into their swing. They all use hip snap and hip rotation.