What the article also didn't consider a widely used definition of the term high-functioning autism. It is often defined in terms of capacity to live autonomously at a level close to someone without autism with minimal support.
If we think of the condition in these terms I believe it's usefulness as a diagnosis becomes far more apparent. It would also allow for explicit recognition that the way people experience autism can significantly change when they are given support that nurtures independence and effective strategies to live.
I personally think that the people coming up with diagnostic frameworks could learn a lot from the The Capability Approach to well-being that has gained some prominence in recent philosophical discussions of the topic. Reading articles on diagnostics that do not seem to take into account the existence of such positions is frustrating because they seem to be missing an obvious way of being more effective in helping people as well as more descriptive.