For me it depends where on the spectrum they are and how old they are. Some older people are totally normal for my definition of normal and would have hard time to explain difference between them and just some introvert.

Sadly I know few kids with autism and while I know that it is autism, to tell you the truth they seam stupid (low inteligence) or something like that. They do not speak, there is no reasoning with them, no explanation from them even at 5 yo.

I usually doubt it is just autism and think there must be some teauma too, since their parents are not really good parents.

I hope they will learn to speak or communicate in some way, because like this they will not be able to take care of themselves.