It's probably not possible that fb has zero data on non users, for example they no doubt have faces in pictures that don't match up to fb profiles. But it is po

It's probably not possible that fb has zero data on non users, for example they no doubt have faces in pictures that don't match up to fb profiles. But it is possible that they don't attempt to collate that data in a way that identifies specific individuals who aren't on the platform, e.g. they don't do anything with those unmatched faces.