See also W. Brendel and M. Bethge. "Approximating CNNs with bag-of-local-features models works surprisingly well on ImageNet." https://arxiv.org/abs/1904.00760 (which is referenced in this paper) and explains "[t]his suggests that the improvements of DNNs over previous bag-of-feature classifiers in the last few years is mostly achieved by better fine-tuning rather than by qualitatively different decision strategies."