Yes, I agree, it is shallow, that's because it is an overview and as the title says, they focus on the reasons of developing stutter. if you're interested in a thorough understand of this topic, research and contemporary therapies, [here is the PumMed link to the peer reviewed articles and resources](https://www.ncbi.nlm.nih.gov/pubmedhealth/c/pmh_sr/?term=stuttering)