I dont think its about DLA, to be a paralympian you have to have a grading, and that grading would identify a disability that could cause you additional costs and identify additional needs.
But being a paralympian would suggest that you have sufficient functionality to be able to work, excepting again those who have the most serious disabilities.
I am no expert on all the sports but I believe our best female paralympic archer is actually now on the olympic team.
All the paralympic riders have physical impairments only, MS, CP and that long thing that Lee has(!), but some are quite high up the scale of affecting functionality.
Like real life, disability is from minor to major, but is grouped in graded steps.
I have suggested that DLA is structured in a similar manner...
Some of the riders are sponsored, Lee has sponsors and British funding and runs his own horse related business.