Disability is interesting.
Many forms (not DSS) now ask "do you identify as having a disability" or similar -
Many people are not "officially" disabled, as it were, but still have limitations, and there is a huge amount of personal and political stuff around disability.
So people can and do "identify as" disabled - people who another observer might say in their view was not. It's all subjective.
Where it's not something like a diversity form - and material benefits can be gained, then there are objective tests (or they try to be) and there is a certain threshold of disability that needs to be passed.
The interesting one is on some public sector jobs they commit to interviewing anyone who declares they have a disability (but they don't check, obviously).
Anyway.
When there are material benefits, then you need to have an objective test of some type.
Where there are no material benefits, does it matter? Yes, I suppose, if it takes something from someone else e.g. some of their space. Most people would say that "identifying as disabled" when you wanted to use the accessible toilet was a shitty thing to do.
Not sure where I'm going with this really :D just that disability is maybe not such a cut and dried example as it appears at first sight.