Today’s conventional wisdom is that both are spectrums. That means one person’s experience with autism isn’t another person’s experience with autism, and one person’s experience as a member of the LGBT can differ from another’s.
However, that’s what the whole point of the letters in the LGBT is. You could be a lesbian, asexual, aromantic, a lesbian who is aromantic, an asexual who is trans, and so on. Someone I know (who inspired me to ask this) has said they began to question why this isn’t done regarding people with autism due to constantly seeing multiple people fight over things people do due to their autism because the people in the conflict don’t understand each others’ experiences but continue to use the label “autism”.
One side would say “sorry, it’s an autism habit.”
“I have autism too, but you don’t see me doing that.”
“Maybe your autism isn’t my autism.”
“No, you’re just using it as a crutch.”
My friend responded to this by making a prototype for an autism equivalent to the LGBT system and says they no longer encourage the “umbrella term” in places like their servers because it has become a constant point of contention, with them maintaining their system is better even if it’s currently faulty in some way.
But what’s being asked is, why isn’t this how it’s done mainstream? Is there some kind of benefit to using the umbrella term “autism” that makes it superior/preferred to deconstructing it? Or has society just not thought too much about it?
I think there are a couple of points to this. Autism started out as a medical or psychological diagnosis. Whereas the folks behind the LGBT term explicitly created it as an umbrella term in the beginning, with the intention to include as many folks as possible.
Within LGBT, it’s possible to apply multiple labels to oneself - as in your examples (an asexual transexual or an aromatic lesbian).
This used to be possible inside of the autistic spectrum to agree as well, but the labels were less clear. E.g. What was the difference between Aspergers and autism? Where do folks who have non-verbal learning disorder fit on the scale - or is this the wrong scale? Do we count folks who have BAP (Broader Autistic Phenotype)? While high functioning autism vs low functioning autism was easier to define, it was taken as insulting.
So eventually everything just got the one label, but that blurred the differences. Which made it somewhat more difficult to talk about.