I think it's a safety thing. For instance, when I played with it, I was at a golf course (winter time here). Since I wasn't ready to trust drawing the waypoints ahead of time, I flew manually to each point and set it. My first waypoint is on the tee box, while my last point is on the green where the Phantom is currently at. It doesn't follow the track backwards, instead it goes directly there without any changes in elevation. So on a dogleg hole, it could potentially fly right in to a tree if I'm not high enough. It may be hard to judge at that distance how clear you are of obstacles.