Otherwise like many others this makes me think that Google is still doing something fishy here and I don't trust it.
Edit: For anyone curious what I am talking about https://webkit.org/blog/8943/privacy-preserving-ad-click-att...
They'll categorize websites (as they already do) and put you into that category, but forego tracking exactly which website/page put you there. The specific page is probably more granularity and privacy invading than they need to continue printing money. Think Netflix movie categorization; who cares which movie I watched put me into the Norwegian-Horror-Romance-Action category, as long as my preferences are known, targeting will continue working.
While it's great for debugging how someone got into a bucket, all that's really needed is the bucket, not the raindrop. I'm certain they'd like to continue knowing those buckets though, so getting ahead of that is critical to their business.
It is in Google's best interest that whatever system they use works regardless of browser.
Largely I agree but Google's relationship with Mozilla and Apple is a little more complicated than "arch-rivals".