Those are a big part of it, it’s also that our brain chemistry interacts with stimulants differently.

One of the major effects of stimulants is the increase in availability of dopamine. The under-stimulated feeling comes from a lack of dopamine due to the reward system not functioning properly in ADHD. When the stimulant forces a release of dopamine it’s not as “stimulating” to an ADHD brain that didn’t have much dopamine to begin with, whereas a neurotypical person experiences a huge abundance of dopamine and feels incredibly stimulated and energized.