Well it’s takes years to get put in the right category. Using various point systems depending on your body and the sport concerned. So there’s no way able bodied person could
Just fake not moving an arm say and qualify.
To be honest though you could technically apply this argument to transgenderism, since it's impossible to change sex. Whether someone is or isn't female, and whether someone does or doesn't have a disability doesn't come into it at all, though.
The reasoning I mainly come across IRL seems to be that people who identify as trans are extremely fragile and distressed, and so we should do anything we can do to be a cushion and to alleviate their suffering.
Online, the reasoning I come across tends to be that the M/F categories should be predicated solely on 'gender identity' rather than on their traditional definitions (linked to sex). Of course transactivists rarely spell out the fact that they are pushing a wholesale and inorganic change of definition, because that would get people's backs up (I would have more respect for them if they were just honest, really, but admitting the artificiality of this would clearly decimate the support they've got from people who have bought into nebulous transactivist rhetoric).
So either way, if we roll out the logic that transactivists are using, you could well argue that whether we see someone as disabled or not should hinge only on how they see themselves, and that to avoid causing mental distress in these people, we should agree that they are disabled when they are not.
(We've seen the seeds of this with Labour arguing you can self-identify as autistic, BAME, disabled.)
However, very few people do actually believe the logic that transactivists are using and it'll probably remain sex-specific without being rolled out to other spheres of identity. These people are playing along because it either serves their ends (big pharma, contempt of women, etc) or because they don't want to put their head above the parapet. I think that's why we won't see the rise of transableism on this sort of scale.