It's not.

Now it is not considered neither a separate unit nor a subset of autism. (As there is no meaningful distinction between Asperger Syndrome and Autism without cognitive impairment.)

Because when Asperger defined “autistic psychopathy” under the Nazi regime, there was a range between the “good” kind whose “special abilities” were sufficient in relation to their social deficiencies to be valuable to society and the “bad” kind where they weren't; the former were protected for their usefulness and the latter murdered (“euthanized”, officially), often at Asperger’s personal direction and entirely based on the social dangers he warned about from them, by the Nazis. So until quite recently, “Asperger’s Syndrome” persisted as the name for “good” autism.

We need more sub-types of such a wide-ranging disorder, not fewer. It's likely autism includes combinations of several types of distinct issues anyway.

As opposed to Asperger seen as a Nazi war criminal?

https://www.scientificamerican.com/article/the-truth-about-h...

That label seriously offends some people.