Yes I'm not contradicting that; the reduced blood flow would maintain the stuttering due to dysfunction of the neurons obviously. But what do you think caused the disruption in the first place? In people with strokes or an oxygen deficiency at birth or severe mutations thst cause reduced blood flow it is very neurological. But this group is a relatively small group and many (especially the ones that can talk fluently alone or sing) have disrupted speech due to some negative social anxiety that is not being acknowledged and being worked around. If I would stop using my left arm for the coming 5 years from now on, you would measure reduced blood flow to certain parts in my right hemisphere. And this would for sure impact my arm usage when I would try to use it again. And if I have a very strong (subconscious) belief that the 'normal' usage of my arm would inflict some kind of social pain (just like we think the same with stuttering, even though we try to convince ourselves we don't), it would be very difficult to use it normally again.