When I came back to United States from South America in 1993 I noticed that US players didn’t train like we did. Rhythm, balance, coordination, all aspects of “athletic movement” were not really incorporated into trainings.
I believe that when learning skills, coaches should really to train all potential movements, being dynamic and creative in the design with the goal of increasing reaction time, activating/ integrating multiple muscle groups through flexibility and force, and creating situations for re-orientation and decision-making on the playing field.
Being dogmatic in one method is never a good idea and I don’t think it’s “harmful” to teach. So if you are coach or a young keeper that just refuses to teach this, maybe you should reconsider. The more tools the better, right?