I’m pretty sure the old Privacy Sandbox was called FLoC, wasn’t it? This is definitely part of Google’s continued efforts to kill the (third-party) cookie in such a way that tracking your user activity will still be possible, but that Google itself will maximally benefit from because they’re the ones controlling how it’ll get implemented.
And given Google’s near-unilateral control of web browsing standards, who will say no? Their biggest partners? Mozilla?