Stochastic wage fixing is still wage fixing
I always ask myself, as to the legality or ethics, would this survive review by a jury of my peers...
you are not allowed to tell anyone how much you make so you might be in trouble if your found out but the companies share this info without your consent. From my POV make it all transparent.
It's not like Glassdoor is restricted to employees, they even offer specific services to employers.
(Got the link from a comment on another recent HN post, IIRC.)