[tyingq]

The EFF summarizes it this way:

"If you are a website owner, your site will automatically be included in FLoC calculations if it accesses the FLoC API or if Chrome detects that it serves ads."

Personally, I don't trust Google that much. Chrome knows which websites I've been to, so it could easily (accidentally, or on purpose) just include any site. Google also has a history of starting conservatively, then rolling out stuff a little at a time. "Boiling Frogs".

Rolling out the header everywhere seems like a good way to keep Google honest about it. Chrome can obviously still do whatever it wants, but it would be harder to explain for them if they shared info on an explicitly opted-out site visit.

It's also just a sort of ceremonial way of expressing dissent with the idea in general. In a way that people could collect statistics on and track.