Whether he is considered disabled in the eyes of the IRS depends if he meets their definition. If he does, then you can select disabled; if he does not, then check none of these apply.
According to the 2020 Instructions for Form 1040:
Permanently and totally disabled. A person is permanently and totally disabled if, at any time in 2020, the person can't engage in any substantial gainful activity because of a physical or mental condition and a doctor has determined that this condition has lasted or can be expected to last continuously for at least a year or can be expected to lead to death.
