There's actually some weird medical correlations there. I have a friend who's a med student and he mentioned that it has to do with autism's comorbidity with autoimmune disorders that require them to take a fuckton of antibiotics - these antibiotics often kill off gut flora which leads to bowel problems. I think autism and autoimmune stuff might be linked genes or something? Don't quote me on that but it's something to that effect.
Someone on twitter posted an article about fecal transplants for autistic people and was REEEEEing about how THESE EVIL DOCTORS WANT US FUCKING DEAD HOW COULD THEY and he had to calmly explain that fecal transplants are the only way to restore gut flora after antibiotics wipe them out and they literally admitted they didn't even read the article, they just assumed it was calling for autistic genocide. These fucking people swing so hard away from autism as a medical disorder that they completely ignore the correlations with other physical issues that have serious relevance for autistic people living healthy lives.