"The clinical diagnosis for a mental illness is that it impacts your life in a negative way."
While ADHD has a large part to play in causing mental illness, and is often misdiagnosed as bipolar, BPD, anxiety, etc, ADHD in itself it is not a mental illness, but a disability. I know this is somewhat a semantic debate, but it is important.
"If someone is managing their ADHD it doesn’t mean they don’t have it."
So someone who is managing their ADHD via medication doesn't have it? What about changing their occupation to one where intricate planning is no longer required of them, so they cease to be constantly failing?
Someone can have ADHD and have it impact their life to a much greater or lesser extent based purely on the life situation they are in.
ADHD is the result of physical differences in the brain. You could be managing as well as a neurotypical individual, but that doesn’t mean you’re no longer someone with ADHD.
You are born this way. Such as someone on the ASD spectrum.
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.