I just was never under the impression that asperger's (even functional asperger's) was something that could be minor enough to be undiagnosed.

That happens all the time. That's the reason why there are more diagnoses today than in the past. I wasn't diagnosed until my mid-20s myself. People just assumed that it was just me being strange. That my school problems were just being lazy or being bored with classes. They thought i was just "strange", but didn't consider any label, other than a diagnosis of ADD at one point.