Similar experience here. As a kid I couldn't manage to read a couple paragraphs on a boring subject but I could study and practice programming for 12 hours straight. Developed plenty of coping mechanisms and was only diagnosed in adulthood halfway into medical school. Every ADHD patient I've seen has a similar story of hyperattention...

I'm convinced this disorder is named after attention and hyperactivity because the children don't adapt well to school. At least not the traditional mass education model where kids sit in a class listening to lectures all day. There's probably a lot more we don't know about it. Some doctors I've seen think it's a made up illness created to sell amphetamines.