You can study the resistance of
torso rotation on yourself. You don't need to watch Oscar to do it. I concede that for certain types of flatwater racing, extreme torso rotation is good, as is some leg pumping and some butt swiveling. Those can be combined into the astoundingly smooth and fast forward progress of an Olympic flatwater kayak, something that we competition oarsmen envy.
I am not trying to prove that torso rotation is useless. I am trying to correct the slavish worship of marked torso rotation when advising ordinary but usually fairly competent paddlers on the reasons for injury. The reason for common hand, wrist, elbow, and shoulder problems of kayakers is NOT a failure to worship at the altar of Oscar Torso Rotation.
I agree with your point that wrist problems often start at the wrist. In ww paddling, paddle feather has been reduced, sometimes to zero, and there are some good reasons for this. Just in my own case, however, I find that feather in the 60 to 75 degree range helps me avoid two-handed gripping of the shaft and consequent ischemia leading to cramping. But it would not work that way for others, I'm sure.