@Alexis_WordsUnbound The problem is the math. If your measure contains a component of one thing on both axes, it will look like there is a correlation even if that correlation is not there.
Like, one axis shows "respondents with high confidence" and the other shows "respondents with high confidence ranked by their skill level in independent assessment", then you'd need to correct for that before concluding.
And from what I heard, this was not done.
But of course, the finding does fit with a suspicion most people have, so there is some bias in favor of accepting it. And once that happens, there is survivorship bias in favor of noticing examples where it fits.
There could just be some set of people so confident (privileged) that they believe themselves to be elite, and that belief makes them accept shallow understanding as complete, leading them to become confident nincompoops.
This would also explain observations, and wouldn't be a general tendency of all unskilled people or of all confident people.