The difference between Dunning-Kruger effect and OverLordGoldDragon effect is that humans naturally exhibit some level of confidence and self-reflection while LLMs may not model confidence and self-reflection at all. Thus they hallucinate when asked to self-reflect on their confidence. Asking the test subjects to self-reflect on confidence about a topic is exactly how Dunning and Kruger found their effect. Hallucinated answers of LLMs should not be taken at face value, because this is where the LLM will likely be inconsistent.
What good is it, if an LLM answers that it is "very confident" as often as it answers "not confident at all" when asked the very same question multiple times? You won't be able to determine the actual confidence of an LLM that does not model confidence from its hallucinations.