The vast amount of treatment for autism is therapies.
It really doesn't matter if the underlying cause is very different in terms of treatment because a speech therapist works the same with a kid with autism as they do with a kid with down syndrome.
If there were more pharmaceutical interventions then I might care a bit more. But there's just not.
In terms of the research, the researchers already have tools to sort and filter individuals based on their specific set of symptoms. Just because 2 people share an autism diagnosis doesn't really impact the research.
What objection do you have other than not liking that it's not a "pure" diagnosis?