I would imagine that they are either deleting it entirely internally or selectively deleting the data entirely in localities where the law requires them to do s

I would imagine that they are either deleting it entirely internally or selectively deleting the data entirely in localities where the law requires them to do so. So far, only the EU has strict regulations requiring businesses to comply with valid requests to delete personal information. (EU GDPR) From a Facebook-makes-money-from-retaining-user-data perspective, I would imagine they are making every effort to ensure they're permanently deleting user data only where legally compelled to do so.