Unfortunately you are wrong. The teacher is right.

Yes, technical details come after the kid knows all the notes in a piece and even memorizes them. The finger and wrist movement you talked about belong to details. These are not easy to do well, and it even takes years of practice to master them. For beginners, it is very hard to incorporate details if they don't know which note to play. You should feel lucky that your teacher already starts to teach your son those techiques. Some teachers (especially American teachers) don't even pay attention to those details until much later. I bet your new teacher will teach in the same way.