Training on adversarial examples doesn't solve the fundamental problem, it merely tries to plug the holes. But in such high dimensional spaces there are many many holes to be plugged. :)

Agreed the failure mode may seem esoteric, but note that OpenAI is making a big deal about them.

A non-esoteric way to demonstrate the lack of generalization is to feed a deep conv network real world images (from outside the dataset). Grab a camera and upload your own photo. Roboticists who try to use deep conv nets as real world vision systems see these failures all the time.