I would imagine there are some cases where it's clear that the person is unable to perform the duties they had in their workplace, and then there are other cases where it's not so clear. Mental health, addictions, and these sorts of things may be not obvious.
Can you give me some idea of how that assessment is made? If there is a disagreement between what the employee is saying they're able to do and what the employer is saying they should be able to do, how is that resolved?