I keep reading that the DSM5 took us from 3 diagnoses to 1. While that is true in one sense, it also established a dimensional scale where any diagnosed person should fall into one of 9 categories. And it’s not a simple matter of severe or mild, but what combination of severity along the 2 principal criteria.
People who describe themselves as having Aspergers are not mild in both areas, but moderate in Restricted, Repetitive Behaviors. PDD-NOS was mild for RRBs. There are people with severe RRBs who turn out to be fully capable of communicating given the right tool.
Now I’m not a psychiatrist, but as a parent I think the application for these levels is that we hope to scaffold development from one level to the next, not trying to jump from where we are to “normal” in one go.
Text in triangles is paraphrased from DSM5 p. 52