Earlier quoted context omitted.
No, why? "Illness" sometimes is about the quantity, not the quality. If you enjoy the odd glass of wine once a week, you're fine, if you drink every hour of the day, not so fine.
But that's an orthogonal concern. Two people can easily display exactly the same quantity of, shall we say, ADHD-like tendencies. If one of them is a success for separate reasons, and the other one is a failure for separate reasons, why do we want to say that the failure, in addition to his other problems, also has ADHD? What do we learn from that? If the success has a lot more ADHD-tendency than the failure, how do…
The criteria is more like “but for this tendency, the patient would be/feel better, all else being equal.” A software engineer making $$$ could meet the criteria if their inability to focus keeps costing them promotions, launch their own company, or whatever their goal might be. A neurotypical buggy whip maker who can’t find or hold a job doesn’t qualify, even if he is obviously worse off overall.