It says that when you are incompetent at something then the skills you lack are the very same skills that you need to assess whether someone is incompetent at it or not. Therefore incompetent people are unable to realise how bad they are at something and often believe themselves to be much better than they are.
For example a really bad photographer can't judge whether a photograph is good or bad BECAUSE he's a bad photographer so he might well think his own pictures are excellent when a photographer who actually knows what he's doing would judge them as terrible.
"No man but a blockhead ever wrote except for money." Samuel Johnson.
Our multisite study on transitioning new nurse graduates didn't bear this out. The inexperienced new graduates rated their own competence much lower than their seasoned preceptors (mentors) rated them. Similarly, another large similation study at NCSBN found that new graduates rated their own readiness to practice significantly lower than their seasoned preceptors did. I am skeptical.
You are confusing inexperienced with incompetent. All the psychological studies bear the phenomenon out. In the case of your nurses they may be inexperienced but I assume that they have been trained. That training will have given them some of the tools necessary to assess their competence.
The Dunning Kruger effect is about people like the "self-taught" car mechanic who believes he can fix your problems better than someone qualified or the father who cuts his kids hair making a complete mess of it because "anyone can do it" or that clown who wrote Gwynne's Grammar or... I don't know... for example... an utterly unqualified buffoon who thinks he can run a country only to find out that the job is much harder than expected but who bashes on anyway in the certainty that he is right about everything. If I were a betting man I'd lay money that the last scenario is where Geoff has come across it as it's been getting a lot of publicity recently.
"No man but a blockhead ever wrote except for money." Samuel Johnson.
