Isolation between sites is not sufficient - collaborating sites (and everyone colllaborates with e.g. Google analytics or the hundred other tracking sites) coul

Isolation between sites is not sufficient - collaborating sites (and everyone colllaborates with e.g. Google analytics or the hundred other tracking sites) could have an ifrane that would abuse cache. You need isolation by primary site, and i don’t remember the exact issues, but there’s some obstacles over there that need addressing (and that browsers do address, but which result in the cache-hardly-ever-used situation we are in today).