Tiger, I don't disagree with your explanation. However, on the last few HD's that showed ambient temps, the ambient temp showing on the bike was within a degree or so of actual ambient. It's possible to receive an actual, accurate reading on a motorcycle no matter the external contributors. Yes, you get a higher reading in the city vs the country but that's normal no matter what you drive/ride.
Temperature accuracy isn't that important anyway...if you are set on riding, would outside temp stop you?... but it would be nice if it weren't off that much.