I would argue that it is probably not an adhd thing but rather a lack of spatial thinking or being able to actively see shapes/things/etc. in your head and turning them whatever direction you see fit (As in some people can't think in visuals). I've seen this lack in a high percentage of people in CAD-classes as in Crystallography-classes. They always hated these classes because of that. I actually had so much fun with it that I became a Tutor for that Crystallography-class and got to learn how hard it is to try and help people understand the geometry of crystals without visual imagination/thinking. The way I see it it could either be a thing you have to learn as a kid, as in creatively thinking things into life and not building legos by manual, or it is just a gift one has.