My experience with new CS grads was that most of them greatly overestimated what they knew, or alternatively, underestimated how much they did not know.
Software engineers tend to repeat the mantra "you cannot make accurate time estimates". That is true regardless of experience level, and everyone seems to be off by about the same amount. So there we have evidence that people overestimate their skills at every level, and its not that different.
Ie I was once perfect for a project except for point 7 out of 10 which was experience with Keycloak (if you’re higher via an HR dept it’s even worse, they just tick boxes, who cares if you are smart and have broad knowledge).
So I’m now proudly Dunning-Krugering around, and use LLMs for super-charged learning. If I underestimated something I take the cost/time myself. So far it hasn’t happened to a significant degree.
But even if it is entirely caused by normal distribution variance, that doesn't make it a mirage, it gives you a reason.