Actually though it blocks all the targeting. So, for example (and you can try it yourself now -- it's live in the High Sierra beta that you can download right now), when you go to Facebook, you will no longer see ads that are targeted to your interests/sites you've visited. Facebook makes it's money off of ads that are personalized -- generic ads don't sell. Same with Google's Ad network -- it's targeting you based on demos that it will no longer be able to track. Yes, Apple may be protecting its users but this is a direct hit at Google and Facebook's ad revenues, particularly on mobile, where Safari has a much higher browser share. Download it yourself and try it out; it really is fascinating to see the difference.