That sounds like illegal wage fixing to me. Companies should not be able to disclose this kind of information to each other and twisting an employees arm to consent to such disclosure is questionable. Employees don't get enough information to do similar tactics to maximize their salaries so the end result is keeping salaries artificially low.

I think constant wage fixing has actually backfired for big tech. The savings in pay they have made might be an impressive number but it is very little compared to what they leave on the table whenever they fail at a software eating the world project, and they end up with a lot more competition from companies that can afford to match their compensation despite operating in much smaller markets and having very little profit relatively.