That is not at all what that law is saying. You can absolutely pay differently based on "bona fide factors" such as experience and job performance. Do you really think everyone with the title "software engineer" at a huge company varying from 0-20 YOE is going to be paid the same? No, they will be positioned differently within a salary band based on experience and job performance. You have clearly never managed a large team or organization and done comp planning for them.