Thoughts != Attention

You're supposed to focus on <task> but you keep thinking those dumb thoughts instead. That's where the deficit comes from.

But, like, I have more of the opposite problem caused by ADHD: I focus too hard on <thing> and literally everything else stops existing. Then 10 hours later I "wake up" and realize I wasted 10 hours doing <thing> instead of just 30 minutes as intended.