Tamura Sensei is one of my all-time favorites.
Did he train in something else that changed his aikido, or did he just develop naturally? Perhaps he trained in some sort of sword based art?
I've thought about that too. What made me think about it was that the skill he shows in his partner weapons stuff (jo as well as bokken) is amazing. I think there is something to this question, and I wonder if the Kuroda connection is only part of the answer as to where that skill came from.
The other thing that is unusual about him is the emphasis on qigong that he had. He discussed it in interviews, and spent a lot of time on it in some of the videos of seminars he taught (like having the class do the Eight Brocades). Clearly he believed (I think he is right on) that picking up such types of trainings is congruent with O-sensei's teachings-- but that does not answer the question of in particular
what trainings he looked into, and who/what were his sources of education in them.
Regarding the other thing, where he stops students and shows a correction. I know from a Western point of view this is pretty bad teaching. But, I think it is a step up from how he was taught-- that's another way to look at it. He is actually making very clear demonstrations in my opinion. Mostly, when people don't "move from their center" he naturally stops their efforts. He does yield several times in the videos I've seen, when people do better, indicating that he isn't simply being a jerk.
My favorite thing he does is that sometimes he shows something wrong, and uke doesn't move. Then, he does it right. So I think he is being a pretty nice teacher actually. (I'll have to find an example)
But ultimately, I agree that he is leaving it up to the student to fill in the very big blank of "what is the difference between what he is doing and 'regular' movement?"