Can't agree with this. Except in situations where the coach makes a casual remark, like ''swing down and through the ball,'' but doesn't continue to badger the player or make an issue of it. I understand that sometimes it's better to ignore and the problem will disappear.
But otherwise, if I'm a travel coach and know a parent has told his/her kid to smile, nod and ignore me, I'm pretty upset. Instead, have the kid or the parent come to me and say, "I don't trust that particular hitting instruction. Hitting coach is saying something else. It's causing conflict.''
That way, it can be worked out. Otherwise, the parent is coaching the kid, not the travel coach. Maybe I'm naive, but I believe in as much open, honest discussion as possible. If a head coach can't handle that, he/she is not a very good coach.
In most cases there should be a conversation between the parent and coach, I absolutely agree. That doesn't always happen before the kid has been given swing tips. With both of my kids, they have been given bad advice (squish the bug, swing level, don't let the rear shoulder drop, etc., etc.) before I have been able to create that buffer. Then again, I'm dealing with rec league and mediocre HS ball, which is a bit different than TB.
If my DD was on a TB team, I would have a conversation with the coach right from the beginning. When I am the coach, I ALWAYS ask the parents about hitting instructors and whether it's okay for me to teach them.