"Do CIFAR-10 Classifiers Generalize to CIFAR-10?" - https://arxiv.org/abs/1806.00451
They use the same procedure used to construct CIFAR-10 to construct a new test set and test a bunch of state of the art results on the new test set.
They see a generalization gap, but the relative order of SoTA results remains (roughly) the same.
So, yes, test set validation is an overestimate of real-world performance of these systems, but progress on test sets is indicative of progress in real-world settings.
And to remember this in context, no-one is asking "do traditional computer vision systems understand images", because they were explicitly just looking at image statistics.