if you're in a country where healthcare costs to the individual can be considerable, someone who's disability costs them extra money would need additional funds to get to a baseline of living. Eg I don't need a wheelchair to get around, so my cost of living does not include buying and maintaining a wheelchair. Someone who does would need to pay for that somehow.

People are still expected to work with UBI. Disability is for people whose ability to work is impacted. They don't even have the option to work, or must do so to a lower degree than previously able.

That being said, I can see the argument to reduce disability in the event of UBI.