Plus Berlin sets up many other variables to make it more conducive to a world record setting time... good pacers, the fastest runners, people holding bottles so the runners don't have to slow. They essentially build a time trial type event. I'm sure there are other locations that could net the same time, but they don't. I would not be surprised if the logistics and weather were equal, that the WR could be set in Chicago or many other courses.
I'd be more curious if age groupers have faster times at Berlin compared to say, Chicago, Tokyo, Frankfurt etc. Since they have the same issues at Berlin as any other event (getting water cups, crowds and so on).