As sfeng describes in another comment, the math isn't right, but the concept does make sense. It doesn't negate what you're saying either though; the 5 point landing is basically a way of distributing the force over as much area as possible. (You can't accomplish the same thing by just landing on your side, because the mass of your body isn't evenly distributed across the surface that would contact the ground.) It does manage to distribute the force over time a bit too, which is also beneficial, but a less significant effect.
