If I’m not mistaken, this also ensures that when you sign out of Gmail, you are signed out of Chrome (no?). That seems like a win for user privacy, insofar as it addresses the likely failure mode of mistakenly leaving the browser signed in after signing out of the website.
No. Pauses sync but doesn't sign out Chrome. So a person could still see your history/bookmarks/passwords in the logged-in browser. They just can't wipe your cloud data (which I think was the same before this update).
Yes I was thinking about chrome profiles. My mistake. But from what I remember, when you choose to log out, Chrome prompts you if you want to wipe your local data. So logging out locally allows you to protect some data. I think there was a way to log out remotely (tricky/weird way), though again without the local-wipe prompt.
I also just tried signing in to chrome (69.0.3497.100), and it tried to sync immediately again, so I'm not sure where the "sync is optional" idea comes from?
