My idea of what Dan and others like him practice is separate from Aikido technique. The way we train incorporates internal development with our understanding of the principles of Aikido. It is very interesting to us and maybe to others.
Dan himself doesn't teach Aikido technique becuase he doesn't have, and doesn't pretend to have, the background--though lots of senior Aikido teachers have found his insights into Aikido waza extremely valuable.
My own teacher is one of several who do train the internal skills Dan promotes as part of their Aikido. The fit is very natural. You might almost think Aikido was invented to exploit these skills.