I think the general reason for that is more about the turntable. There are always going to be hot and cold spots in a microwave just based on how they work, they can’t eliminate them. So spinning the food around means that sometimes it is in a hot spot and sometimes in a cold spot… Except the very center where it is basically just rotating in place. It is either going to be a hot or a cold spot more than likely, and whatever food is stuck there is going to burn or never cook.