Those ads are targetable by categories determined from private data, but Facebook doesn't give anyone else the data, that's literally why people would purchase ads through their exchange and not through another exchange.
Google has the same model, they don't sell your data, they use your data to match you with advertisers through a fairly opaque interface that lets advertisers reach the categories of people they want to reach, without revealing the data to allowed them to put someone in that category.
Kind of like how your Mom will set you up on a blind date based on what she knows about what both parties want, but doesn't disclose all your information because she doesn't want anyone to be upset with her.
Those ads are targetable by categories determined from private data, but Facebook doesn't give anyone else the data, that's literally why people would purchase ads through their exchange and not through another exchange.
Google has the same model, they don't sell your data, they use your data to match you with advertisers through a fairly opaque interface that lets advertisers reach the categories of people they want to reach, without revealing the data to allowed them to put someone in that category.
Kind of like how your Mom will set you up on a blind date based on what she knows about what both parties want, but doesn't disclose all your information because she doesn't want anyone to be upset with her.