Earlier quoted context omitted.
It's very easy to diagnose someone with extreme autism, just as it's easy to diagnose someone with extreme dwarfism. It's blurrier when you get to mild autism (and mild shortness) where there is less visible impairment, less obvious behavior, and often visible benefits.
I'm 1.93 and my knees make trouble. can you give me a diagnosis? :D I'm reading a book at the moment, in german, "Ich liebe einen Asperger" and even proper autism was barely recognized by people working with kids 15yrs ago: "... but it couldn't be Autism!?" is one quote from an educator about the family's most autistic child. Things probably haven't changed that much. One other thing, even though it is exhausting, ki…
Severe autism has symptoms like nonverbality (unless treated with years of intensive communication therapy), extreme repetitive behaviors (tapping, bouncing, etc), and freakouts/meltdowns in response to unexpected situations and sensory inputs, of the sort of intensity and sensitivity well beyond what you'd see in the average person over the age of about 7years.
In years past people might not have been able to pinpoint "autism", but disregarding the minor important of the label, it was still easy to see a lot of what was going on with the person with the condition. (Effective _treatment_ is of course much harder than mere diagnosis.)