He seems more deliberate about his stepping in later videos. No idea if that's a gongfu thing, a performance thing, or just whatever mood he was in the day these videos were taken (my guess is the latter).
Having watched many of these and knowing him I have always believed this is a situation of performance/video. No matter how great we are at something like this we still have our concerns and worries. In this case we can see that on most of the demonstration videos low stances are avoided, as well as really active kicks and one legged stances. In terms of kicks the foot is always put down directly after which is not the way the form requires, single leg stances are not sustained or just outright avoided. Basically every precarious position, and every strenuous approach is avoided. I believe it is in the service of making a successful video with whatever desired appearance is made possible by avoiding those things, such as sitting up more straight, not wobbling or struggling to maintain a position, and not getting exhausted outright so that many takes can be achieved.
These ideas are coming from my understanding of him as well as my own experience trying to make videos. Low stances (in this style) basically wreck the performer after half a take and contribute to fatigue, failure and unexpected errors in other actions, just exhausting. My guess is that this was already take number 13. I have the original disc recordings of these demonstrations, and on one of them he starts yelling at someone and the camera cuts, then he is nervously looking around. I think that was his son getting loose and invading the shot if I remember correctly. On these videos above you can see him looking off camera at the same small individual if you pay attention.
In my experience there is most often something that interrupts any good shot, often environmental or situation. Much of time it is one's own error's due to fatigue or camera anxiety so such variables must be reduced. A video like this is just sort of a walk through of the form and the style, because the real practice is near impossible to capture well.