This is what I observe from the video:
1. When bowing (in seiza) to the shomen and to the class, Chiba's palms were pointing up (0.04). This gesture symbolizes the "opening of the heart" -- a sign of humility.
2. At 0.08 and 0.36, instead of the normal standing bow, he used the mushin (no-mind) gassho -- a form of greetings use in most Buddhist communities across the globe. He does this greeting/bowing most of the time.
3. After the demo at 0.33, he sort of took a sumo-stance and bowed touching the floor with the tips of his fingers and with his palms facing the class and then straightened up into a natural stance. By that gesture, he could be telling the class, "That's it, please practice".
I am not his student and neither have I attended his seminars, I guess that he expects less formality compared to some other shihans. When Toshiyuki Arai shihan from Gunma Aikikai visited our dojo a few years ago, he commented that students can practice more with the time utilized for all the formal bowings. He suggested that the formality of bowing be restricted to the opening and closing of the class only.