Very hard to understand the meat behind all the fluff of the article, especially as the simulation code is not available, and as the presented simulated and original graphs are effectively the same (I don't see a disagreement).
It's clear that the perceived curve will be differently sloped, as no one will evaluate themselves as the topmost or the bottommost percentiles, so the edges will be biased.
And if in both cases we draw differences between perceived and actual, we will get the same curve that everyone knows, biased or not.
Huh? The point is that the two graphs come out looking the same, making the original no more meaningful than random.
Source code is here: https://github.com/pem725/Dunning-Kruger (found here: https://pem725.github.io)
It's annoying they didn't plot the new and old "perceived" curves on the same figure, but if you pay attention to the y-axis, there is a very big difference.
In the old plot, the bottom quartile has about a 50 percentage point margin between actual and perceived performance while the new one is 30 percentage points, which is a 50% difference between the old and new curve. The second quartile has 3x more margin in the old version relative to the new one.