I feel like people who "aren't functionally impaired" are often just extremely good at masking, and don't notice all the problems they deal with anymore. So it's more like, they won't diagnose or treat you because you've adapted to your limitations too well.
I had to do this with my ADHD. If I told people I struggle a lot, but I can get by with a million calendar alerts and reminders, they just tell me to go home. But if I phrased it instead as, I struggle severely with remembering things and meeting deadlines and appointments, they're more interested. Then they ask if I have any supports, and I say calender reminders help a bit, but don't resolve the underlying issue. Same problem, different presentation, with an emphasis on what I can't do.
It sucks we have to do this to get noticed, but also I think autistic people like myself are prone to being "too honest" with doctors and accidentally down-playing our struggles. Like oh yeah I just don't understand social norms at all, but I get by and figure it out you know? Instead of, actually this often makes life really hard and is a huge barrier especially if I'm in a new environment.