I saw this interview on your channel a few days back and really enjoyed it. I can't comment on his ideas about developing focal dystonia but I agree with what he was saying about excess tension in general. I injured my scapula area muscles on my right side many years ago from holding too much tension there, practicing way too long, not stretching, and then suddenly deciding to do push-ups even though my muscles were worn out and I was out of shape. Unfortunately, once you have scar tissue it's a long term problem. Mine has eased up some over the years with time and massage but has remained a problem ever since. If there's an upside, it's that I've learned to be more aware of the excess/disfunctional tension in my playing and am now hyper vigilent in getting students to be careful and learn to recognize it in their own playing.
Thanks for doing these interviews.