I have no idea--that's why I'm skeptical and would love to see evidence. In some of these companies, veteran outlier high-performers end up getting promoted several times to things like "Distinguished Engineer" and have enormous staffs of engineers reporting to them. They are executives in all but title, so I'd expect them to be in the executive pay bands and get executive salaries. Those aren't the people we're talking about. We are talking about regular "top performer" individual contributors (write code as their job, no direct reports). Why would a company artificially keep them at some low promotion level but pay them as if they were multiple levels higher?