Individualism and the Two Disability Stereotypes

I think there are two main disability stereotypes, which I call the able-disabled and unable-disabled. The able-disabled is the person who despite their disability, can do X, Y and Z, who overcomes their disability to do those things, while the unable-disabled can't do those things and lives a miserable, limited or otherwise pitiful life. Our society has a tendency to split people up this way.
When I try to think of examples, I think of specific people for the able-disabled stereotype - Hellen Keller, for example. When I think of examples for the second stereotype, I think of generic groups - low functioning autistic, for example. Why is this?
I think society, when looking at people viewed as able-disabled, view them as unique and special individuals, who have individual qualities responsible for their success. They are the exceptions. Some say these special qualities are modifiable, others don't, but in any case this person is special, and not just as a euphemism for disabled.
However, even if they describe a specific person for the unable-disabled stereotype, the person is not viewed as individual but as representing a group. They are an example rather than an exception. So the person themselves is not considered important, rather they represent a group of people. Also, the focus is mostly on their disability, and if they mention personal qualities thought to be separate from the disability, it is in terms that suggest shades of the able-disabled portrayal (since the same individual is often described in both ways).
An example of this shift is with many parent descriptions of disabled children. I often wondered why certain behavioral traits were in among the various health problems and such whereas others were at the end. The reason is that they are viewed as problems due to the disability, or as positive traits despite the disability. Here's the typical format:

My child has X. I thought things were fine until [xe regressed/xe was born not breathing, or funny looking, or whatever/xe was X age and not doing Y] Currently, xe has T, U, V, W, X, Y and Z. All that makes it sound really bad, but xe [is a wonderful, happy person/can do X, Y, Z/has taught me so much/has greatly enriched my life].

Basically, it starts out describing the child with the unable-disabled format (which is the basic format for describing disability) then at the "All that makes it sound really bad, but" they switch to the able-disabled format. The specific order may vary, but it's remarkably similar. Parents often don't consider the able-disabled exceptions as such, but as exceptional, relative to most people (which is often described as rubbing off on siblings, parents (though they'll often give examples of why they're not perfect) or other people who know their child.
In that framework, it seems to me that often person-first language is intending to encourage an able-disabled view of disabled people, where the disability is peripheral. But why can't the disability be central without viewing the person as pitiful? For example, why split up behavioral traits into bad, disability related things and good, individual qualities?
When I look at behavioral traits, I often forget about good or bad and just accept what is without value judgements. I don't wonder if the hyperactivity of the Rett girl I work with is good or bad, or assume it is bad, but just think of it as a trait I have to plan for and react to (for example, by recognizing that being with her is tiring and not planning for strenuous things right afterwards).
Ettina