[JabavuAdams]

The thing is that last D. A mental difference is not necessarily a disorder. That depends on severity and extrinsic factors.

E.g. there are cultures where punctuality is not really a thing. I'm not saying we don't gain many benefits from a culture of punctuality and reliability, or that one would necessarily want to live in one of these cultures. I'm just expanding on the author's point about extrinsic factors. Difference can often be a disorder, but difference is not equal to disorder.