This is one of my personal pet peeves. All the "instruction" people throw at batter's while they're at the plate goes overboard sometimes. A lot of it just drivel, with no bearing in real-world hitting mechanics, and most of it isn't going to do anything more than confuse a kid. Practice your mechanics in practice. Execute during the games. Keep your mind clear and focused and keep things as simple as possible!
All I can figure is that a coach wants to let everybody know he's a coach so, by golly, he has to do some some coaching to let everyone know! Then, if the kid does something good, it looks like the coach was the reason, but if the kid does something bad...well, then, the kid just messed up on her own.
There is a flip side of this coin. Some coaches don't speak up when they really need to. I see this all the time and saw it a few times this weekend.
Runner on base and the base coach says absolutely nothing to her about the situation, the number of outs, what to do on a fly ball or line drive, tagging up, etc. Then the runner gets herself doubled up on a line drive, or doesn't tag up and advance on a fly ball and the coach goes ballistic on the runner! Coach, there's a reason we let you guys stand on the field in your special little coaching boxes. It's to instruct the runners! You can't just assume that every runner knows what to do in every possible situation.
All the "coaching" that goes on while kids are batting might just confuse them more, but a little coaching while they're just standing there on the base, with plenty of time before the ball gets put into play, keeps them focused and on the same page.