Note that this 9th circuit ruling merely stated that pointing to the use of prior pay isn't an automatic win for the defense - this just let the plaintiff go back to lower court and try the case. The case is still ongoing, the plaintiff has not won the case.
Rizzo v. Yovino, 9th Circuit ruling, indicates that basing present pay on past pay may violate the Equal Pay Act of 1963 (https://www.forbes.com/sites/ericbachman/2020/03/13/past-sal...).
... but more importantly, this case has entangled the Fresno County public school system for over a decade. That's expensive relative to the alternative of... Not doing that.