Hmmmm..... not to take either side, but I don't see Akuzawa doing anything with that bend at .30 other than make the point that he's getting below Uke's force before he uses the ground path to go up Uke's arms. Since he only does it that one time, it's obviously just explicative and not something he commonly does. There's a couple of other things I might nitpick myself, but not when someone is simply trying to discuss and show the various factors that go into an action.
I see what you mean. Like I said it's easy to misinterpret video (especially with no sound to help). But what I was referring to is something I see all the time in aikido, especially beginners but also in people who have come to aikido from another physical activity that relies on 'conventional strength/power' (it needn't be a martial art). Namely: the tendency to leave your backside behind when moving forwards. Amusingly you also see it when moving backwards, a good example of which would be practicing okuriashi in kendo where people have the same tendency except it appears that they are increasing the gap between their hands and their navel as they move backwards. But it's the same thing. It's most commonly/obviously seen in aikido IME with tenkan ikkyo.