It doesn't sounds like you've actually tried this.
It doesn't sign you into anything but the google website, just like before. You have to turn on browser sync to sign into the browser. Seriously, try it. Your passwords, history, etc aren't there, and nothing shows up in your history from that session. Signing out of gmail still signs you out.
The new system is annoying because it makes it more difficult (impossible?) to sync to one Google account while having another one be the primary signed in one, but it doesn't sign the browser into anything on its own.