Well..

The thing is that no matter what you call it my observation is that most people claiming to do rear kicks are way wide. That is all. And they are two distinct kicks. Chuck Norris for example clearly is not tucking the leg. And neither are most kenpo peole. So no matter what the terms just watch videos of people and watch people in class. Someone doing an actual rear kick and not a back kick is the exception to the rule. And there is a time when a back kick would be a better option. So they are two distinct kicks. For example if a person is positioned with their feet already apart and there is not time to pproperly chamber tight to the central axis then a back kick would be the move by default. So they are two different moves.