ENF, it does seem pretty quickly sensible (to you and me at least...heh) that a 'disability' would be something over which the person has virtually or literally no control.
Missing limbs or other body parts etc.
But as has been noted, many jurisdictions have expanded 'our' definition with a range of latitude.
All in all, just another reminder of why in 21st century America a business should very carefully decide just how much they wish to expand with Employees rather than via other methods such as outsourcing jobs to private contractors. The rules are often quite different.
Your own profession recognizes that of course. Many jobs that prior to say the 1980s are outsourced to contractors rather than to employees (actual members of the official US armed forces.