No, it wouldn't, because employers have a strong incentive to hide salary band violations, while employees have a strong incentive to discover when negotiations are possible.
> it strikes me as an extraordinary to claim successfully negotiating higher-than-average wages is typical.
Then you should probably go talk to somebody who made that claim. But it's a nonsensical claim, so my guess is not many would be making it.
I've never been a typical employee in my life. I have, however, been the highest-paid non-manager (or so I was told; this might have been an attempt to shame me into working more for free) in a hundred-person development group, well out of band, because I brought capabilities and skills to the table that they needed more than they needed to Maintain The Integrity Of The Salary Band.
And calling me "anonymous" is kind of funny.