hey Xue,
tell me what you think of these thoughts. I have to admit, I never really "got" taiji and I finally stopped doing it altogether. I think my training with my current white crane sifu has given me some insights that might help me understand what I'm seeing in taiji a bit better than I had before.
What I'm seeing when I watch this video is all the movements, whether it's a turn, rotation, step, shift, they all begin with the feet and legs. That is what "drives" the movement, the power of the legs and feet actively engaging to propel. The difference being, what I believe most people who do not understand taiji well, and who are really just doing it for fun and exercise, they initiate the movement from the top-down, starting with the shoulders they turn and move and shift, and they kinda step "late" to keep a prop under the torso. This is in contrast to actually driving the movement with the feet. Visually, it's a subtle distinction and would be overlooked and missed by anyone who isn't clued into it.
Does that make sense? and I correct in what I think I see?