The retrofit is, as I said, an after-the-fact construction. It is always supplemental—always not-original. The retrofit is additional. But as a supplement, to retrofit is to fix in some way. Like eugenic design, a retrofit can be meant not to fit a need, but to make its user perform and behave in a particular way, often in a constrained way.
I would just add, recalling the idea that “all technology is assistive technology” (p.86), this characterization of the retrofit as supplemental and not-original shouldn't mislead us into imagining that the construction to which it is supplemental is not itself supplemental (and rather "original").
Dolmage's point has to be: The construction, prior to being retrofitted to "accommodate disability", is already inherently eugenic, and the retrofit merely extends and confirms this.
That is, if the initial construction is already an artificial project of "normalization" and exclusion (moreover one that tends to be thought of as "natural"), retrofitting this construction to "include" abnormality/disability amounts to coercion: it either highlights the fact that these people don't belong (normalization of "us" as opposed to "them"), or it encourages them to try to belong (normalization of "them", i.e. assimilation rather than integration).
Whether we are "accommodating" disability or "excluding" it, in either case we are concealing the fact that "we" (i.e. the more or less "able-bodied" and "able-minded") have always already been accommodated ourselves, and that this accommodation is far from "natural".
Which is to say, in other words, that there is no such thing as "natural ability" or, again, "independence". The illusion (delusion) that these things exist is historically, socially, politically, racially, economically (etc.) determined.
Or yet again, there is no such thing finally as "belonging". No one essentially belongs anywhere. "We ", as "we", belong--but this process of coming-to-belong is too often reducible to normalization.
Judith Butler and Bernard Stielger are crucial references, for me, in this regard.