The conservative commentator Thomas Sowell has an interesting book on children who start talking late; he had such a child himself.
Good for your mom. Nowadays it's the other way around--a lot of parents my wife deals with WANT their kids to have the autism diagnosis, simply because they believe that this will enable them to get their kids some treatment and some medication. We are such a pill-centric society that many people believe that all solutions are found in a bottle of medicine. Parents can't accept the fact that their kid, for whatever reason, has a behavior problem, or a learning difficulty. They demand that they get a diagnosis of autism. It's really discouraging to watch this kind of behavior--even moreso, I'd imagine, for parents whose kids really DO have autism.