I believe that anything that affects speech and language processing may lead to disfluencies. Research indicates that PWS may exhibit challenges in word retrieval and language processing. Research has found that PWS may have differences in attention, working memory, and executive functions, which are involved in language formulation and production. Studies suggest that PWS may experience inefficiencies in retrieving the motor programs needed for speech sounds and syllables. Impairments in motor program retrieval might be more pronounced when speech becomes more linguistically complex. We might experience greater difficulties with longer or less familiar words or sentences. Factors like anxiety and cognitive load further exacerbates motor program retrieval difficulties. You mentioned the terms 'dysnomia' and 'anomia.' Dysnomia refers to difficulty in recalling words, while anomia specifically relates to difficulty in finding the right words during speech. Individuals who have dysnomia or anomia tend to be error-prone. Likely, in my viewpoint, if we learn to perceive these errors as negative, needed to be repaired, learn to evoke strong emotions and rely on struggle behaviors, then it may in some cases lead to stuttering-like disfluencies. This is just my take on it