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?
IMO, LGBT descriptors came from that community. Until the autism community develops their own descriptors and hits some critical mass in agreement, it's not any random person's place to develop terms for them.
LGBT communities hit major levels of activity and visibility to the public decades ago. My cousin isn't getting the autism diagnosis she needs today because multiple medical professionals she's been to still think girls can't have autism.
It doesn't surprise me some people like your friend are developing some terms. While people like my cousin and her mom are going to be spending their energy on other priorities.