It says if you want to be successful with the core ranking systems of Google Search, consider these and other aspects of page experience. Ranking *systems* are different than ranking *signals* (systems typically make use of signals). Ranking systems can use ranking signals, but not necessarily all the time or for every query. However, it is a collection of ranking signals that multiple ranking systems can and do use to evaluate and reward pages with good user experience. This isn’t the case for Google Search because not all websites use Google Analytics, and not all users use Chrome.