For the record, the study they're likely citing was the one that tested less than 15 kids, 3 or more of which did NOT have autism, and the then-doctor permanently crippled one of them in the process of testing for the digestive-neural autism link
(The entire study exists because he wanted to discredit a vaccine to sell his own)
Also remember that correlation isn't causation. Trust me, every autistic person in the West has heard all about how we just need to adjust our gut biome and suddenly we won't be autistic, or we just need to go vegan, or any of a thousand other wonder cures. These cures have been touted since the 1900s, and the people they "work" on are generally agreed to just have learnt to mask better because almost every "treatment", no matter how benign, is horrible to deal with.