I agree with you. Learned blocks is another manifestation of stuttering. Somehow PWS noticed that delaying uttering words makes easy perception on the audience. Attempts to interrupt the blocks transfer to different mode of stuttering (prolongation etc.) So, a stutterer is waiting when the word finally shoots from the mouth to his/her relief alas temporal. IMO, the problem is desynchronization between mental word structure and motor apparatus of PWS. That synchronization which normally is automatic, in PWS is vulnerable and prone to emotional status. That’s why PWS speak normally beying alone.