It's perhaps not a disability. But, it is a disabling disorder. It imposes much greater challenge for many tasks that are straightforward for others. I barely graduated high-school on time, I was suspended from a community college for having a 0.6 GPA, and I've failed countless courses I've taken. None of my failures were due to an inability to understand the information; they resulted from challenges with the processes and procedures inherent with formal education.

Although I was suspended from community college, I had no problem teaching myself linear algebra or diff eq. I eventually was able to get a job as a software dev, it took me until age 28, when someone else perhaps could have reached it right out of college. I'm now trying to finish a dual math and comp sci degree in my spare time, and even now I've still failed trivial courses.

I was among the brightest students in my class growing up, but willfully chose to stop taking my ADHD meds in 8th grade. I was a stellar student until then. I've resumed them only very recently, but I have complete confidence that had I chosen to remain on the meds the whole time, I wouldn't have faced all the same challenges.

I don't think the evidence aligns with your understanding.