[arthuredelstein]

Hi! Author of PrivacyTests.org here. Thank you very much for the comment. (I only just saw your reply.) PrivacyTests is very much a work in progress, and all feedback is much appreciated.

GPC does differ from Do Not Track in that the former is intended to carry the weight of law. See for example: https://cheq.ai/blog/what-is-a-global-privacy-control/

Regarding document.referrer, you are absolutely right that there is a cost/reward balance and most browsers have chosen to allow cross-site passing of the referrer. However, there are browsers on Android that do block cross-site referrer altogether (see https://privacytests.org/android.html).

"Media queries" refers to the fingerprinting threat where, for example, screen width and height is divulged. You are right that JavaScript can also be easily used to get screen width and height: any fingerprinting resistance feature should protect against screen fingerprinting via both JS and media queries, in my view. Some browsers already do that, as the results show.

Your question about scale is a good one. Some browsers (such as Firefox and Brave) embed fairly large blocklists. You are right that query parameters can be changed, but in practice I haven't seen any cases of that happening (yet).

As far as I am aware, Safari is (by default) blocking cookies/storage from Google Analytics and similar trackers, but not blocking the scripts themselves. You can see that cookie blocking reflected in the "Tracking cookie protection tests".