Applying the word narcissist to a person with autism, regardless of their level of social functioning, is something of a conflict in terms. They can’t read people very well or even at all with some. Successful manipulators they are not. Grandiose? They do have their fascinations that could appear that way, but it isn’t to impress anyone else, they’re just compelled, it seems.
I think this psychologist is talking out of his backside too.
Many low level autistics exhibit sympoms of personality disorder along with the autism. Within personality disorder, there are a multitude of variations including narcissm. His diagnosis sounds reasonable to me.
There are a lot of different meanings of narcissism. "Narcissism" is a pretty good word to use to discribe a more or less "normal" person who's very self-involved and doesn't form relationships with other people. It's of less use in describing psychopathologies and the different senses of the word can get in the way of understanding. With really damaged people it doesn't fit and doesn't get at what's going on in their heads.