It seems a no-brain-er that you wouldn't use the same browser for personally identifying accounts, as you would for anonymous browsing, rather on stay signed into those accounts on the same time. I guess if you used the same browser and didn't delete cookies or logout often it might be easy not to realize you are signed in.

I'm glad that they at least seem to need to fight to determine this information about 3rd party content loading with processor profiling tricks. I would have assumed easier tricks existed.

It's bad enough, the extra opportunity using your anonymous browser for personally identifying accounts would give towards matching you to your account through fingerprinting.