Seeing: document.interestCohort is pretty abhorrent looking. First-class advertising support in a browser is a major turn-off. Google is probably only a few steps away from losing controlling stake in Chromium, and stuff like this certainly will lead others to flock away.
Why is it abhorrent? FLoC doesn't compromise your privacy. It does interest inference client-side, away from bigcorp servers. It doesn't leak any information about you. But all the "privacy" people are totally against it anyway. Why? Because they just hate advertising. The whole "third party cookies are bad" thing has always been a sham: it was never about privacy. It's always been about killing advertising itself.
fetch("mycompany.com/" + mycompanyUsername + "/" + (await document.interestCohort()));
There. Now it's neither anonymous nor client-side anymore.