Autism emerged from Kanner's autistics ("Kanner's Syndrome") which was itself a narrow view of autism and tended to be more extreme in its impairments mainly of social and communication variety...initially had to be separated from schizophrenia (to distinguish that these children were not experiencing psychosis in their odd behaviors) which took a while...but ultimately Kanner was overly exclusive in thinking this was a very rare condition and refused to see it as a spectrum, also refused to see it as inborn, and blamed parents for forcing these special interests and eccentricities on their children in lieu of providing them with unconditional love and affection. His model basically crashed and burned over time, but he did nevertheless make some breakthrough discoveries about these individuals' condition which would be later seen as genetic...and part of the same spectrum as Asperger's.
"Asperger's Syndrome" emerged from Asperger's patients who were older than Kanner's...they were more verbal, could communicate very well compared to Kanner's Syndrome children, and tended more towards over-linguisticism than paucity of language, but nevertheless seemed "autistic" to him due to their focus on their own inner worlds, lack of friendships with other children, literalness and logicality of mind...but wouldn't have fit in with Kanner's Syndrome group.
So you can see that Kanner had a very limited view of Autism and likely it did encompass the more severe and low-functioning cases, but at the same time you can see he honed in on peculiar or remarkable cases, where the children had sometimes very extreme and seemingly useless abilities (on the savant spectrum), sometimes of prodigious levels (autistic children who had memorized great amounts of information which he attributed to, again, parenting style which valued such useless information due to flaws in the parents, rather than genetic neurological differences that granted these children special gifts).
They were two very different models that kind of came together over time. I think today, the vast majority of cases diagnosed "autistic" are in fact more Aspergian in nature. Nevertheless I think the idea that it's a spectrum -- Asperger's idea initially -- does hold up well, and he would have accepted Kanner's group into his although probably wouldn't have called them "little professors" and might've had another name for them. If someone knows about this maybe they can chime in here, I still have relatively cursory knowledge of all this on some level...but I'm always trying to learn more.
FWIW I'm about half way through Neurotribes (which has been my resource for some of the above info), which is a really interesting book! I've read a handful of books on Autism, AS, etc., but I think this one is my favorite so far...very comprehensive and well-written.