From the abstract:
"Paradoxically, improving the skills of participants, and thus increasing their metacognitive competence, helped them recognize the limitations of their abilities."
All they found was a statistical artefact.
You can just have a look at the big picture at the top of the Wikipedia article: https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
> Relation between average self-perceived performance and average actual performance on a college exam.[1] The red area shows the tendency of low performers to overestimate their abilities. Nevertheless, low performers' self-assessment is lower than that of high performers.
So regression towards the mean explain the entire effect.
See also https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect#...
This is still very much compatible with my claim that unskilled people profit from being reminded (repeatedly, not just in the exam at the end of the semester) that they know less than they think. I will avoid conflating this with the Dunning-Kruger effect in the future (Thanks!).
An recent study found that medical students' estimate of their own intelligence gets lower right after taking an IQ test (confirming the better-than-average effect). But one week later, their self-estimated intelligence returns back to their pre-test levels. To me this suggests that students (and all others) will overestimate their abilities - and invest less time in learning - if they are not constantly given feedback.
https://www.sciencedirect.com/science/article/abs/pii/S01918...