If you don't stutter when you are alone, is it all in your head?

If you don't stutter when you are alone, is it all in your head? I personally don't stutter when i'm reading alone in my room, so I guess that means that I don't actually genetically stutter? It's all in my head so I guess speech therapy is not the right way but I should rather go to a psychiatrist? I'm saying this because I recently read an interesting book about overcoming stuttering by Oscar Hausdorfer who says: Almost(!) all people who stutter dont stutter when they speak alone so therefore the theory that stuttering is something neurological is not true. People who stutter should only work on the mental side of stuttering and no speech therapy can help because this will only reinforce the narative in their head that they speak in a wrong way.