Dick was a perfectionist. He had the uncanny ability to spot a spec of dust on one frame of film as it went through the 'dailies' projector at the studio. No-one else could see it but he would.
He would then rant and rave and insist on a re-shoot... even though it was quite likely that the scene took two days to shoot in the first place and no-one in the world would see what he saw. (He was invariably right about seeing it however!) His quest for perfection was both his greatest friend and his ultimate enemy of course... in the sense that he was repeatedly fired from major productions (beyond his own creation) for being behind time and over budget. But 'genius'?... yes, he was... and probably still is, wherever he is and whatever he is doing right now. I owe everything in my career to him and could never replace the fantastic two years I had as his personal assistant/apprentice and the subsequent five years I was a director/animator for him at the studio. (By the way, the sequence you are talking about in the documentary... where he criticised the assitant's inbetweens... that was Dick on his best behaviour for the cameras! I could tell you stories about how he could really tear into unfortunate employees for far, far less reason!)
Maybe one day someone will write the definitive book on Dick that will lay out the truth and the tragedy of his life. (s)