It's true. I think it's a good way to show how you can get beyond the limitations of your intuition. Here's how I think you can look at the problem: First, note that there is energy available from wind blowing over the ground. Windmills work. Next, make a free-body diagram of the machine going downwind faster than the wind. There's road force on the wheel, drag force on the vehicle, and aerodynamic force on the prop. Now look at power at the wheel and at the prop. Power at the wheel is ground speed times the force at the wheel; power at the prop is airspeed times the force at the prop. The thing is going downwind, so ground speed is greater than airspeed. The intuitive breakthrough is to see that the wheels are driving the prop: not the other way around. The difference between those powers is available to counter the drag. If you know the drag coefficient (and what was defined as the reference area), you can calculate how fast it can go. I'm sorry I never met Andy Bauer. He was a very cool guy.
It's swept wings that don't make sense to me.