I was told by psychiatrists etc that I couldn't have AS since I had a (then) fiance, was at university and had friends. They also said they were not experts in ASD's. These were speculations from professionals, not part of a diagnostic assessment. I never got assessed on the nhs (UK).
After a few years of failed attempts to get assessed at all, I ended up paying privately for assessment. I got a proper assessment and was diagnosed with AS a month ago.
My opinion was always that I would accept a diagnosis (or a negative diagnosis e.g. not having AS) when I was assessed by professionals who could then explain their decision to me based on my traits (or lack of) and knowledge of AS. If they couldn't do this, they surely couldn't be knowledgeable enough in AS to make the decision.
It's annoying though when people assume AS = no friends, no higher education etc. Unfortunately it happens all the time and not just with AS. I'm curently reading about dyslexia and I'm fascinated to discover the amazing different abilities in dyslexic thinking and the implications, when previously I joined the vast majority of non-dyslexic people in thinking, 'Dyslexia is the lack of ability to read and write'. People say to dyslexic people, 'But you have a degree, you can read, how can you claim to be dyslexic?' Similar scenario to us with AS or suspected AS. People think, 'AS is inability in being social' and they say, 'But you have a husband and a job, how can you have AS?'
That said, part of the diagnosis is to do with having the traits of AS cause real-time problems. For me it's unemployment, currently, and only just getting my degree after some written warnings, things like that. If someone has AS except that it wasn't giving them any clinically significant problems, I guess that could be a professional reason to say, 'You are doing ok, you don't have AS'. But ideally that would need to be explained and discussed very well, with clear knowledge of AS.