If Mozilla enables it by default but "offers a way to turn it off", this would still count as enabling FLoC. Google could enable FLoC in Chromium by default an

If Mozilla enables it by default but "offers a way to turn it off", this would still count as enabling FLoC. Google could enable FLoC in Chromium by default and then, correct me if I am wrong, the browsers based on Chromium would have to disable it. Mozilla of course is not based on Chromium. However, Mozilla does try to match Chrome feature for feature and Google also is the hand that feeds Mozilla.