I still pace and move a lot when I am thinking hard, especially when I'm not in class, and I still whisper sometimes when I read questions... I also have a lower working memory compared with how quickly I think, so it may be a way to cope with that/compensate, as JoyceJ pointed out. It's only caused issues once in two decades of schooling, and I don't fall onto the spectrum in any other way. My guess is that it's just some quirks...