The old footage of O Sensei with Terry Dobson. At one point O Sensei appears to discuss and apply "ki" and send Dobson very sleepy. Compliant, faking, hypnosis, something else explainable by physics?
I haven't seen the video, so I can't comment specifically.
But that doesn't sound like a martial arts technique to me, so I think the question of its validity falls outside the scope of this conversation, unless it can be convincingly asserted that what makes O Sensei's hypnosis work is the same thing that makes a kotegaeshi work.