The misdiagnosis, imo, is due to outward (often regarded as negative) behavior displayed by boys. Girls, as a rule, tend to internalize things, including being socially/emotionally aware of others.
Generally speaking, girls don't tend to draw attention on them to stand out like a sore thumb. IF girls get unwarranted attention, they risk being isolated and/or being labelled - social, emotional, and/or physical consequences are too much and not worth the risk for many girls. Some girls if they've got ADD/ADHD or are on the spectrum may lack this social awareness or connections to risk taking behavior, but they're the exception, imo.
Some boys (who then become Steve Jobs types) are not so internally motivated (or perhaps neurologically wired) to curtail their behavior, which others may deem as outrageous and socially unacceptable. Though that doesn't mean they're not sensitive or care what others think. And, no, Jobs was never diagnosed with ADD/ADHD but he was definitely off the wall and an out of the box type.
