I’ve never questioned it; no psychiatric or psychological professional who has ever evaluated J has ever questioned it; no one who has actually met J has ever questioned it.
But a couple of non-autism experts who haven’t met him have questioned J’s autism. They’ve either wondered whether J is at the functioning level I report him at, or (!) whether he’s autistic at all. Surprisingly, these folks are themselves autism parents.
Most autism parents have had to put up with people (regular folks and professionals alike) questioning their intuitions and insights about their own kids. So surely autism parents, of all people, know better than to question, at least publicly, the parental intuitions and insights of their peers in autism parenting? 
There are, however, a few things about J that some people who think they know something about autism and who haven’t actually met J find it hard to wrap their heads around.
One is that J is a combination of high functioning in terms of expressive language skills and life skills, and moderate (not mild) in terms of social engagement and comprehension skills .
He can speak in complex sentences; he can express conditionals and hypotheticals; he can embed one complex concept inside another. For at least a decade now, there’s no analytical proposition or logical argument or idea that has occurred to him that is too complex for him to put into words . He can navigate the city on foot and by public transportation and successfully carry out transactions in stores and with neighbors (our basement is filled with the discarded fans that he has persuaded people, often without our knowledge, to give to him). He recently graduated from college with a double degree in math and computer science and just a few accommodations (mostly written transcripts of lectures and the option to do some of his work online).
Some people hear all that and assume he’s got Asperger’s.
But J has no real friends, nor any interest in having any. He still mostly tunes out of the conversations around him. And his reading comprehension skills are quite limited: he’s about as far as you can get from the prototypical Aspy bookworm. His vocabulary is still way below normal, and his sentences, however complex, do not reach the heights of verbal eloquence seen in many of the most vocal individuals at the “mild” end of the autism spectrum. J, indeed, has had multiple psychological evaluations, and the one thing that has remained stable over all the years, for all his tremendous progress, is his level of measured autism: moderate, not mild.
Some people assume that J must have some debilitating sensory issues—as, they assume, all autistic kids do. Furthermore, J is deaf. Indeed, not only is he deaf, but he seems to have very little sense of smell. And he doesn’t like dirt on his skin or coming into contact with slimy substances like shampoo or deodorant. And there are a number of foods he won’t eat because of their textures. And, of course, he likes the visual stimulation of spinning fan blades. But none of this impedes his ability to function. The implant is a miracle cure for deafness; there’s no environment he’s afraid to explore; at restaurants, there’s always something he’ll eat. He has no trouble making sense of the sensory information around him.
When I think of autism parents questioning J’s diagnosis, I’m mostly thinking of one person. This particular person started out as a friendly acquaintance. When I was seeking parents to interview for my NSF project, she volunteered, opening up about her own situation (her daughter is non-speaking and, no, does not use facilitated communication). I remember suggesting some ways that she might use her daughter’s AAC devise as a bridge to literacy, and I remember her seeming to appreciate those suggestions.
But about a year later, in a thread on a social media post, she started to question my son’s diagnosis, and things went south from there.
Like me, she’s incensed at the small group of highly articulate individuals who identify as autistic (an indeterminate number of them self-diagnosed) who dominate the discourse about neurodiversity and autism and lecture us autism parents on all the ways in which we, purportedly, are misunderstanding and mistreating our children. But unlike me, she, generalizing from this highly salient subset of the so-called autistic, believes that all individuals who are “high functioning” in terms of their autism also have communication skills that are not only high functioning for autism, but also high functioning period—i.e., high functioning compared to people in general. When I presented J as a counterexample, she challenged me. She suggested that such a counterexample (high functioning yet moderately, not mildly autistic; high functioning overall, yet still below-average linguistically) couldn’t exist. She showed no interest in learning more about my son, who does exist. The exchange ended unpleasantly and left me baffled and dismayed.
Of course, most of my friction with fellow autism parents involves those who use or endorse FC. Some of these people have claimed that I know nothing about autism beyond what I know about my son. Somehow I must have duped the college professionals who have hired me to design and teach courses on autism, along with the academic journals and book publishers who have published, many times over, what I’ve written about autism.
For these sorts of parents, J is also problematic, but for different reasons. He doesn’t write poetry about the world he sees through his special autism-inflected sensory system, nor does he produce ruminations about autism and advocacy statements about disability and communication rights. He prefers to ask questions about hypothetical crime scenarios or time travel paradoxes or… ceiling fans.
And he learned language the hard way: not by sponging it up invisibly over the years and then letting it out through his extended finger once a keyboard was finally held up to it, but through many years of intensive, systematic instruction.
The kind of instruction that turns some moderate, not mild, autistic children into individuals who overall are quite high functioning—even as they continue to be moderately, not mildly, autistic.
 Even we autism parents who question the validity of the FCed output of the FCed kids of other autism parents reserve our criticisms for the pseudoscientific issues involved. We do not second-guess those parental insights and intuitions that don’t appear to have been warped by quackery and pseudoscience.
 Both J’s social engagement and his comprehension continue to improve by the day.
 I attribute J’s much higher-than-expected expressive language skills, and the improving comprehension skills that seem to be coming along for the ride, to the SentenceWeaver program I created, originally for him, but which is now expanding the language skills of many other kids.