What you suggest sounds analogous to a flywheel. You’re using the mass of the vehicle to stabilise your speed and drive the propellor when the energy stored in

What you suggest sounds analogous to a flywheel. You’re using the mass of the vehicle to stabilise your speed and drive the propellor when the energy stored in your momentum > the energy you get from the wind. However, this does not account for the full experience they are describing where you can attain speeds far greater than wind speed. If that’s the case there must be a different “angle” to it, pun intended. He’s not just harnessing the purely linear “push” from the wind. There must be other vectors superimposing. Could well be the lift provided by the Bernoulli effect on the propellor blades. As I mentioned elsewhere once you get to that level it’s all very domain specific.