"When the person visiting a website featuring Facebook’s tools is not a registered Facebook user, Facebook does not have information identifying that individual, and it does not create profiles for this individual.
...
We do not create profiles for non-Facebook users, nor do we use browser and app logs for non-Facebook users to show targeted ads from our advertisers to them or otherwise seek to personalize the content they see. However, we may take the opportunity to show a general ad that is unrelated to the attributes of the person or an ad encouraging the non-user to sign up for Facebook."
https://www.judiciary.senate.gov/meetings/facebook-social-me...
It's conceivable that Facebook could deanonymize users/aggregate the data they get from like buttons etc, but they claim that they don't use that data for ad targeting and it's only used for security.