I'm trying to read the book, but the basic argument seems to be that Clausewitz didn't see the need for an independent air force, so that settles it.
The fact that Claus-O popped his clogs shortly after the Rainhill Trials is apparently irrelevant. As is the fact that the record of his recommended kind of war (invade the enemy's lands and disarm his forces) has, in the industrial age, been mixed at best, up to and including the recent SWA unpleasantness.
But then I don't have a PhD so WTFDIK.