That's my question as well, they aren't saying anything about shadow profiles. It seems like a ploy to get people to create accounts just to 'stop' tracking.
If you read the article linked in the comments, it looks like this works by creating a special tracking ID for each user that can be disconnected from the real UID, if the user chooses to.
So if you don't have FB, presumably you already don't have UID, so you're on equal footing with Facebook users that use this future. They are tracked, but tracking data is not connected to their UIDs.
If you don't have a facebook account, facebook likely has a shadow profile for you. Which would carry your phone number, full name, and whatever else they could extract from your friends' phonebooks and whatever other sources they use. There is no opting out of that, and there is no opting out of facebook getting third party data that lets them connect your shadow profile to a cookie, or to information collected by third parties.
From what I understand, it will actually create a shadow profile not linked to your real profile, instead of actually not tracking you. (I have the french version, which basically says : 'you can disconnect tracking informations from your actual account if you desire')
So there's no change for people not using facebook, you'll be tracked like before no matter what.
So if you don't have FB, presumably you already don't have UID, so you're on equal footing with Facebook users that use this future. They are tracked, but tracking data is not connected to their UIDs.