Certainly there are things such as you describe that are learned from experience. No question. OTOH, instructor X might have a much better understanding of what is really happening in a windmill motion and be much better able to teach it even though they never played. Not necessarily of course but the list of elite performers who could not teach their particular skill is endless. Find the best mechanics teacher for Tammy ten year old you can find regardless of whether or not they played. As she ages, she should pick the brain of every elite pitcher she can. That first teacher needs to be someone who she enjoys or at least who doesn't make it miserable for her.