Unless your teacher is inexperienced, usually he/she knows what he/she is talking about. Sometimes, it is best to at least try what the teacher is advising you to do - if the change doesn't work, it is just as easy to go back - little harm done. Trust your teacher. While it is true that not everyone plays in the center, many do. I've had several students who were decent players slightly to one side or the other that found improvements when changing to the center. It is physically the best spot for airflow unless the teeth/mouth layout implies a different direct path for airflow.