It would be good to footnote this as one of many theories, or maybe on piece of the puzzle. I've always been sceptical of physiological reasons as the security of my own stutter has varied through my life according to stages of confidence. When I'm more confident stages, stemming from my job, life-work balance, and living environment being good, I don't tend to stutter at all, and vis versa. If it solely was a physical cause I.e. just a lack of blood to a certain part of my brain, then surly my confidence wouldn't be able to change that as much as confidence can't make an autistic person not autistic