Yep, just wanted to write that exact same reply. It was one or two weeks ago and asked for permission to unlink YouTube, GMail, etc... from each other (as I understood it, when "opting out", login with the same Google account will still work, but they're not allowed to share data for ad profiling, recommendations etc...)
> Your data from all Google services, regardless of whether they are linked, may still be shared across all services for certain purposes, like preventing fraud, protecting against spam and abuse, and complying with the law.