That's not even what the original study claimed to find though! It caught on because it seems so intuitive, yes, but the specific curve of confidence vs. skill doesn't seem to look like that at all.
This is how memes or memetics or just language works though. Things often get called something they aren't and if it sticks it sticks. I'm not saying it's correct or whatever, just that it stuck because it vaguely gave a name for something people experience and didn't have a name for before.
Look through any etymological dictionary and you'll see this phenomenon. What does a computer have to do with "to strike" in PIE? Something! But it's not the literal meaning.
