As someone with ADHD I'd describe the experience more like profound boredem with everything in life. You seek obsession because you can't generate excitement for normal activities on your own
I think attention modulation disorder.. I have the longest AND the shortest attention span ever. I might not finish typing this but also I'll research black holes unblinkingly for 16 hours.
The biggest impact from my adhd is actually a shorter than average short term memory span. Mine was found to be about 8.5 second, with the average humans being 18.
My long term memory is fine, probably better than most but it's getting stuff in there that's the issue.
I don't even think it should be labeled as a disorder. Or at least people should be more aware of what a disorder means. It doesn't necessarily mean there is anything wrong with the person. The behavior just happens to not be suitable for the particular environment they are in and causes difficulties. If you change environments to one that allows that behavior to no longer be a problem then they no longer have a disorder.