Able Disabled and Unable Disabled

I found a post on a list about chromosomal trisomies. The subject was Predicting Outcome - long and as the title suggests, it was a very long post. It's archived in that list's archives, available to the public.
The post is about the perceived differences between mosaic and full trisomy (particularly trisomy 18). It's by Karen, a mother of a boy with mosaic trisomy 18, who talks about all the nasty stuff she's gotten from various people because her son's trisomy is mosaic instead of full. As I read it, I was struck by the parallels between how high functioning and low functioning autism is portrayed.
The post is in response to another woman saying that when she was pregnant she was told mosaic trisomy could be "just as bad or worse" than full trisomy, and later, after the child was born "she is doing so well because she is mosaic".
One of the first things Karen says is that despite the stereotypes, both mosaic and full trisomy kids are very variable. For example:

"I look at the mosaicers on the list, and others that I have met and the variability never ceases to amaze me - and there is no rhyme or reason to any of it. But then I look at the "fulls" and feel the same."

Unlike the division between high functioning and low functioning autistic, the division between mosaic and full trisomy is determined by a medical test. But in both cases, one characteristic is assumed to indicate all sorts of other characteristics, when in fact it doesn't. Definitions of low/high functioning autism vary. If you define it by speech, pretty much every other skill varies between both. Same if you define it by self-care, whether or not they "regressed", whether or not they self-injure, or any other trait.
Karen also describes how doctors often look at her son and see a "great kid", but don't see all the struggles he has. High functioning autism is viewed the same way. An autistic who can speak well is often assumed to have no difficulty communicating, looking after themselves, holding down a job, or anything except for reading nonverbal signals. And autistics who type well on the internet are often assumed, by people who've never met them in person, to be high functioning in all their other skills, if they're even autistic.
Karen also describes how once a person on the list asked about development in trisomy kids, and she described when her son learnt to do various things, and was told she shouldn't discuss her son's development because he was mosaic. Countless times I've been told, or seen others get told, that their experience as an autistic person doesn't matter because they're "high functioning". Granted, sometimes there's a true difference, both in terms of mosaic/full and high/low functioning autism. But a) sometimes the difference is not as great as it's believed to be, and b) everyone's experience counts, even if it's unusual.
And there's more parallels. Basically, this post is to point out the truth of the statement "same struggle, different difference" in yet another circumstance. It seems that there are two disability stereotypes, the "able disabled" (high functioning autistic, mosaic trisomy) and the "unable disabled" (low functioning autistic, full trisomy) and in fact, the truth of what the person is like lies somewhere in between. In Critic of the Dawn, Cal Montgomery names the "able" version of her Mary, and the "unable" version Bruce. She says:

"I choose not to emulate or to repudiate either of my phantom relatives. That decision reflects my understanding that there are those whose lives are dominated, with or without their consent, by phantoms much like Bruce or much like Mary. It reflects my conviction that the representations of disability that give Mary and Bruce detailed life are less than reality, are both more and less than truth, that I am being asked to choose between two stereotypes, not two realities. It reflects the heritage I claim as mine, the community, the communities, to which I believe I am responsible."

Ettina