Comment by chrismorgan

On reviewing that article, I’m actually not certain what the situation is. It seems to suggest that it’s just isolating third-party cookies, but my understanding is that that’s roughly what they shifted to (for at least new users, and maybe that’s the key) a couple of years back. In at least Nightly, when I checked a month or two back, the default Enhanced Tracking Protection mode was Standard mode, which says that it blocks “Cross-site cookies in all windows”—not cross-site tracking cookies, but all third-party cookies.

I’m not sure why there’s so much obscuration around this stuff. I wish there was a caniuse entry on third-party cookies that identified matters clearly.