In my opinion, and in my opinion only. a coach doesn't have to write down everything, every stroke and shot the player made in the rally, that is just nonsense. Rather doing that by video taping them. So a coach just have to write down the weakness of their player and opponent players. And so during the set, they can give their players advice where to hit and what kind of attack they should use. Example, ok your back hand clear is shiettie dont try that shot no more rather than go take a lil more step back to gain more the momentum of the body movement to help the backhand... ect. And yea they do write down weakness and how unaccurate of their players shots so that they can tell them to train later on. Example: drop close to the net, but it's not a good play because the shot travels too slow. Rather making a lil further the net but make the speed faster. So go on and practice that shots. I know you all going to disagree on this example. But of course that is just an example in a specific situation where their opponent stand.