I worked on trying to make a solution for this. I don't think PowerPoint looks at the points of a freeform. It really only looks at one shape to another. I tested this with several attempts. The only way I know how to for sure pull off what you are looking for is some frame by frame animation. I know its not fun to do but it would probably only need about 6 or 8 frames to look fairly smooth. I know it's not ideal, it appears that PowerPoint just does not handle shape points that way. At some point in time (sorry for all the "points" =)) I will have an add-in called framer that could potentially handle the animation of this. Its still in the works but will be coming out at some time. Sorry I don't know of a different solution in the interim.