From my own (negative) experience with SLPs in early childhood, I would just say: Listen. To the parents and to the speech of the PWS. This was over 20 years ago and things have probably and hopefully changed now, but my SLP would practice certain words or sounds with me, which completely missed the point. I think de-stigmatizing stuttering is a worthy goal that benefits all. This would be a job too big for one SLP though and more for the teachers with a PWS (or any person with some kind of disability) in their class though. When your environment constantly shows you that you're an outsider, it makes coping with stuttering very difficult. I do think that, especially with PWS with severe stuttering, only acceptance is generally not enough. Some kind of way to navigate the blocks/repeats as the happen can be greatly beneficial.