It makes sense to me. Transparency benefits the party that is more free to go elsewhere. Lots of companies, fewer good ceos, means that the ceos can leverage this better than the company can.

To put another way - at work, if you knew how much every employee made at work, it would probably be helpful in salary negotiations. Dont see why it would be different for ceos

This[1] Wikipedia article talks about it some, and links to this[2] paper.

[1]https://en.m.wikipedia.org/wiki/Executive_compensation_in_th...

[2]https://www.degruyter.com/document/doi/10.2202/1535-167X.120...

Edit: adding an additional paper on the topic https://www.princeton.edu/~amas/papers/CEODisclosureMandate....

All CEO pay for public companies is exposed in the 10Ks.

What I suspect the person was referring to is the change where compensation became more tied to equity valuation.

CEO pay wasn't always public and the compensation is only mostly equity because it has a tax advantage [1].

[1]: https://americansfortaxfairness.org/tax-fairness-briefing-bo...