It seems to be a worthwhile meta-analysis. However, one cannot prove a negative – absence of evidence is not evidence of absence. For example, the various measures summarized may have been too insensitive to detect a variation. However, it does go against some of the early 2000s studies, such as work by Ann Foundas which was quite splashy at the time. There was previously a summary of Kate Watkins's data back in 2018 or so, which made the same point. The cerebral dominance hypothesis, in which stuttering is due to atypical asymmetry, has had a tendency to recur on a semi-regular basis and I don't expect this to change anytime soon. That said, it has not been a best explanation argument for stuttering for nearly 100 years now!