If they have material nonpublic information about salaries and share it for the purpose of coordinating salaries, then yes, this is or should be illegal price f

If they have material nonpublic information about salaries and share it for the purpose of coordinating salaries, then yes, this is or should be illegal price fixing. They can solve the problem by making the data public, thus giving the same competitive negotiation advantage to the employee. The publicness is the key part -- it's price fixing when They trade information with Each Other, information that is unavailable to You and is essentially valuable to both sides in negotiating an employment offer