There is oncourt coaching of elite male tennis players. Look at Boris/Vajda and Uncle Toni, as well as Muzz's box. Why do you think these guys look up to their boxes after literally every point? Federer never does that, nor do players like Stanimal, Berdych, Monfils, etc.
Boris was openly yelling at Djoker during Cincy 2015 to "move in!" and nothing was said about it. Toni has blatantly coached Nadal for years. None of it makes much difference anyway. Nadal and Djoker would have won just as many majors without getting "advantages" from their coaches.
