Great observation! In my opinion, research does indeed seem to indicate a strong environmental (or [epigenetic](https://www.google.com/search?q=%22epigenetic%22+%22stuttering%22)) factor that contributes to stuttering. As you pointed out, there are likely also other factors other than anxiety.. and I think at (or near) the onset of stuttering, we linked such epigenetic factors to speech performance.. and the longer stuttering persists, the more opportunity we have to associate such environmental stimuli with speech initiation. I think that CWS who don't have a stuttering mother (in your example), might have less strong environmental factors to associate with stuttering. So, I can completely resonate with your idea of there likely being some kind of reason behind "avoiding the initial [speech plan](https://www.google.com/search?q=%22stuttering%22+%22speech+motor+plan%22)" or some purpose to linking triggers to speech performance.