I have posted the vid which elaborated the root cause being our amygdala and as for evidences I don't know what you are getting at since Parry's channel had several vids about Valsalva response. 'And I do see 1000+ people that are cured when followed the course of DF.' 'Being cured' implies they will never stutter for a lifetime but can you guarantee that? If you can evaluate their fluencies at least as 85%, close to normal speakers , in a long term like dozens of years then I will eat my crow. As for curing, Parry's Valsalva therapy is not claiming it can cure your stuttering indeed, but it is improving your Valsalva response and at first and at least you have to prove your diaphram therapy has really 'cured' 1000+ people.