The Paxlovid.com website is from the for profit company Pfizer, which makes Paxlovid, so yes, they'll list every kind of disability that could conceivably be a reason to take paxlovid and make them money.
But yeah ADHD can count as a disability, in some people. That's based not what you have, but if what you have substantially limits at least one major life activity.
While they publish that list, they did not come up with it. That list is from the emergency use authorization granted by the FDA.
You're free to guess whether the FDA is basing that on science, politics, or corruption. I've seen sufficient evidence that they do all three that I don't have a strong opinion. (In this case, I don't think that the science is there.)
But yeah ADHD can count as a disability, in some people. That's based not what you have, but if what you have substantially limits at least one major life activity.