A statement on the post reads, “We’re adding a control that allows users to turn off linking web-based sign in with browser-based sign-in — that way users have more control over their experience. ”
Once this next update drops, users who disable this feature will not be signed into Chrome when they sign into a Google service. There will also be UI changes so that it’s easier to see if you have Sync turned on.
As it is now, when you sign into, say, YouTube, you will also be automatically signed into Chrome. Subsequently signing out of Chrome will also automatically sign you out of YouTube, Gmail and any other Google service you were using.
If you want to have this disabled now and don’t mind going through less user-friendly methods, you can use this method as described by Twitter user The InfoSec Dragon:
In addition to this change, Google will also change the way cookies are cleared. Currently, when clearing cookies, Chrome retains Google authorisation cookies to keep you signed in. With the new update, Chrome will clear absolutely everything, signing you out while you’re at it.
Chrome’s Update 70 is slated to roll out in mid-October.