Chrome would be more likely to implement a persistent and identifiable (to Google alone) tracking cookie replacement and ship it worldwide, which iirc they did — and then cancelled, of course. They seem to be focusing instead on improved tracking of Android users from the kernel up, rather than browsers from the headers down; GrapheneOS is, presumably, viewed as a serious threat to their advertising revenue.
https://privacysandbox.google.com/blog/update-on-plans-for-p...
Yes that's what I'm saying this could be used for. Browser generates a client-side key (or any kind of identifier, possibly derived from the site's TLS cert/domain or some other info) for the current browser/user/device/whatever and just offer that to every website as an extra header so that whoever wants to track you, can.