ADHD is also a designation for a lifelong set of conditions that manifest early in life.

You can end up developing ADHD-like symptoms later in life, but the „late bloom” itself is a good reason to seek and treat underlying conditions.

And to correct a misconception, moving leg is a self stimulation thing. It’s not a hyperactivity manifestation, but a self-grounding action. On its own it’s entirely neurotypical.

„Attention deficit and hyperactivity” designation sits somewhere in the ballpark of „diabetes means your pee is sweet”. Technically correct, easily observable, but ultimately describes symptoms, not the causes underlying them.