It may be that the air flow is more consistent than you might think. We know that it takes less air in the upper register to make the notes speak, and they sound louder than they actually are. They have more “zing” and focus than bottom end notes, and sound louder than they are. Finally, there is very little passive about this etude. The passage is long, the player is using circular breathing (wow!) and he is going for good sound quality, all demanding engagement and active playing. I believe he is playing very efficiently.

By the way, Javier is currently playing on the US version of “Dancing With The Stars,” amongst other things.