The point I gleamed from the article was not that city driving was an easy problem, but rather that freeway driving has unique issues when it comes to reliability and safety. Simply stopping the car could be an acceptable minimal risk condition for a crowd of cyclists and pedestrians, but that's no longer the case in a freeway. On top of having to deal with sensing range + on-board offline decision making + truck stopping distances, having no safe fallback like "just brake" seems like a pretty difficult problem.
There's also the "interesting events + training" argument in the article, which I'd love to see points for or against.
There's also the "interesting events + training" argument in the article, which I'd love to see points for or against.