My nephew wasn't talking and paid no attention whatsoever to anyone but his mother. No repetitive motions, lining up objects, or any of the other classic symptoms of autism; he simply acted like an overgrown infant to whom nobody but Mommy was worth noticing. It was a pretty obvious that the person who examined him didn't know much about autism.
Interestingly, as a kid I exhibited a lot of those classic symptoms. Spinning, sorting and lining things up (I had a seashell collection that would keep me occupied for hours), and only as an adult have I trained myself to look at people's faces when I talk with them. However, I was also talking and reading at age 2. I guess the moral of the story (in both cases) is that you gotta look at the big picture.
I'm glad your son is getting early treatment! I hope it helps him mitigate or overcome his issues, the way it did for my nephew.