Perhaps your man is the exception and he possesses perfect technique and can conserve his mass and speed such that he can deliver them as efficiently in the air as on the ground.
All I can go on is my own empirical observations over the years. Jumping kicks rarely come close to the same level of power as a grounded kick for most people. Why?
- Focus. It's quite difficult to focus all your mass into a striking point when you are adding a variable like leaping into the air also.
- Timing. Same idea as above.
- Loss of momentum. You are converting some of the mechanical energy from the legs and hips into jumping, rather than conserving it for full delivery to a target.
- Loss of stability. Striking while in the air is an inherently unstable proposition. Suppose the target moves slightly or you are off a bit. The power delivery system just isn't forgiving when you are not on the ground with the bracing action given to you.
Compound these problems by adding a SPIN on top of the JUMP and you've magnified the problem even more.
As I said though, one can mitigate these problems by having exceptional technique, but I think just from a pure physical science perspective, the jumping, spinning kicks CANNOT be as powerful as a normal, grounded kick. Any kinesiology majors out there?