Yes, I can agree with you about anxiety and feelings. I think that stuttering, when a person has great awarness of it, which happens usually in school aged children /teens/ went beyond speaking to emotional components. In my experience working with attitudes and emotions lead to more confidence in all social situations and in the speech itself. If you are not confident and you are anxious you avoid stressful situations, and even if you mastered techniques of fluent speech in safe enviroments (clinic, home....) you will not transfer it to everyday life because of it. For me great source is : https://www.uts.edu.au/sites/default/files/2020-07/Stuttering%20and%20its%20Treatment-Eleven%20Lectures%20%28May%202020%29.pdf These are lectures from M. Onslow and they are updated frequently. And with emotions and anxiety great researcher and therapsit is R. Menzies, pschyologist specialised in the field of fluency.