I'll correct myself, the data is simulated and I skipped the word. You are completely right to remind me of this. But there are a few important considerations here.

1. The original DK study used a IQ like score based on general cognitive faculties for its argument, subjective vs. measured.

Wiki quote: "The initial study by David Dunning and Justin Kruger examined the performance and self-assessment of undergraduate students in inductive, deductive, and abductive logical reasoning; English grammar; and appreciation of humor."

2. Second of all, for this I have consulted the study itself, according to my cursory read the sample size of the study seems to be below 100. I'll let that speak for itself.

3. A new study working with more data, that doesn't just present generalised skill shows that, just like in the simulated data, it is still a blob following a normal distribution in terms of density. The simulated data was meant to show how misleading inferences can be made with noisy results.

from https://doi.org/10.1037/rev0000644