Static stretching is bad? What genius said that? Probably something you're presenting out of context I would say. Plus you cannot take something ie: diet or whatever as a reason not to take what that person said seriously in his field of expertise.
Why are you keeping on with amount 'movement'? The subject is doing suwariwaza. What exactly do you mean abt. 'less movement on the knee compared to 'modern'? It seems to me you are saying something which doesn't mean anything. Perhaps you could explain.
There's quite a lot of science showing that static stretching isn't what people used to think it was - here's a brief summary of the issues: http://saveyourself.ca/articles/stretching.php
As for diet not being in his field of expertise, I agree - orthopedics wasn't either.
More movement on the knees means more stress less movement means more stress. The type of movements you see also tend to be different in more modern Aikido - many more turning and spinning movements.