My upper weight coach helped me a ton when we used to wrestle. It's one thing to coach from the side, but another to coach while you are wrestling someone. Feeling their reactions, weight shift, etc. is something almost impossible to do from the sideline. Not that it can't be done, but I think there is a better opportunity to succeed when there is a coach to wrestle with.
Just ask Kyle Snyder why he thinks he is getting better and better.
Plus techniques have to be adjusted or outright changed at various weights. What works for a middleweight isn't the same as what'll work for a heavyweight - there's a reason you don't see as much funk in the upperweights.