Very late comment: I understand it now; someone explained it offline. It's not about what Google says, it's about how others explain what Google says/Googlebot

Very late comment: I understand it now; someone explained it offline. It's not about what Google says, it's about how others explain what Google says/Googlebot does. So Googlebot boosts, for example, sites that load and render quickly, and people explain "you should use X" and a few years later, "you should use Y". I do see how the change from X to Y is arbitrary.