You don't seem to know what ADHD is.
https://www.mayoclinic.org/diseases-conditions/adhd/symptoms...
"Hyperactive means being too active and having too much energy. It may include disruptive behavior."
"Run around or climb in situations when it's not proper."
So why would you not just do the same with pets? Pets soil the common areas of a building, requiring ongoing maintenance that can't always easily be charged back to a particular unit, so I can understand why some rentals would impose surcharges.