I somewhat agree with you. Some parents (I have no intention or right to blame them though) don’t sometimes sense that a lot of the behaviors are for internal and emotional reasons. They usually state, that stimming or self-harming is solely a reaction to sensory input or an action done because you are mentally “ret*d”.
Some of my stimming is purely an action to block the outside and “to get as in as possible”, some is just a reaction to some internal feelings, like excitement or anxiety, some is a reaction to sensory overload. Some stimming actions are there without a particular reason (or at least I can’t articulate the reason).
Some of my stimming is an attempt to relieve anxiety. I do not hit my head, but when I am overly anxious I hit my thighs (I remember reading that autisticnintendofan did the same stuff too) or sometimes I hit my hands together (a bit like clapping but with a force). A milder version is to shake my head from side to side while anxious. The reasons for anxiety can be very many and there are probably as many reasons as there are people, sensing isolation, being frustrated, being treated badly, being hurt, not being able to shift you focus elsewhere otherwise, selfhatred and so on...
I feel that when I was not talking, I was still the same. I think that ultimately that child didn’t change that much, when she learned to talk. All the emotions, all the human needs were there. And sometimes this thought makes me feel extremely sad, cause I know that very many of those who are nonverbal and living in horrible circumstances as completely misunderstood and forgotten, feel and have these same things inside.