Didn't realize their was difference. A more mundane example of hyperfocus for me ADHD related or not that I still couldn't control was in school. I pretty much was unable to force myself to study unless I hit a state of panic when I started university I would usually panic 3-4 days before Paper or test was due. I did pretty well academically this way I quit school when I was unable to panic anymore.
As far as I understand it hyperfocus is not voluntary at all for ADHD individuals, in fact rather the opposite studies have shown that ADHD brains become increasingly less able to focus the more effort the put into trying to focus. Studying for math exam focusing is ridiculously hard when there an emergency at the gym broken wrist, dislocated shoulder then it comes easy.