If you are Google, Amazon, or Facebook and have near infinite data it makes sense to deep learn. But if you have a more modest sample size you may not be buying any accuracy
The author explores sample sizes up to 85, and then suggests this is the relevant range except at Google, Amazon, Facebook, etc.
But the VAST majority of people considering deep learning have sample sizes between those extremes. Results on small samples are interesting, but it's disingenuous to market this as typical of the world outside Google.