Safari doesn't do this (it's part of iCloud, which syncs all docs, not just Safari), and Mozilla doesn't tie signing in to website signing in. I do think this is quantitatively different, esp. considering Google's near monopoly on email accounts.

They are tying website login to browser login, with the intent of merging the two - that's the problem.

To users are Google who are fully invested in that corp having total control of their online life, this fuss will seem quaint and odd, but I do think it will have serious implications long term - people are turning away from search too for similar reasons - abuse your monopoly enough and people will actively seek out other options.