The video is like jumping out of a plane with a parachute on to prove that Newton's calculation of gravity on Earth (9.8m/s2) is wrong. That's just MY take on it. The thrust from the prop makes the chopper go up, but it also pushes DOWN on the board. If the chopper is also attached to the board (as it was in the video)....it'll create a TOUCH more lift than downforce, which is visible when the chopper gets light on its skids. That difference is only there because the board doesn't absorb 100% of the rotor's thrust (because nothing does 100%).