How does the author miss the fact that in his graph the self-estimation hovers around the 50th percentile (as expected with random data), whereas in the DK graph it averages around the 60th to 75th percentile? That is a significant bias.
As a control, the author should have plotted Fig.8, but based on DK's data (or at least estimate how Fig. 8 would look like based on the result in Fig. 3). Then it would have been obvious that the self-estimation error tends more towards overestimation in the lower quartiles than ist does towards underestimation in the higher quartiles - which is exactly what DK's conclusion was.
In essence: this article actually confirms that DK is not just a random statistical artifact.
As a control, the author should have plotted Fig.8, but based on DK's data (or at least estimate how Fig. 8 would look like based on the result in Fig. 3). Then it would have been obvious that the self-estimation error tends more towards overestimation in the lower quartiles than ist does towards underestimation in the higher quartiles - which is exactly what DK's conclusion was.
In essence: this article actually confirms that DK is not just a random statistical artifact.