> In those cases, why is it a "disorder"? Why can't it just be "how some people are"?

It often is:

> It can be helpful to think of ADHD not just as a deficit or disorder but as a ‘difference’.

Especially as it seems to come with positive traits! It goes on to list focus, responding well in a crisis and creativity as common ADHD traits.

https://www.rcpsych.ac.uk/mental-health/mental-illnesses-and...