Current research shows that stuttering is both neurological and hereditary. In short, it's just how our brains are wired; there's a glitch between thinking the thought and saying the thought, and then a lot of mental crap, such as anxiety, can get tied up with it too. I think the problem with models like this one is that they encourage self-blame: if only I did X, Y, Z better; if only that random thing hadn't happened to me, I wouldn't stutter. Personally, I don't think this is helpful. It's too much like the trope that only nervous people stutter. For me, acceptance that this is just how I am, and it's in no way caused by something I did or didn't do, has been very freeing.