The requirement to make GDPR downloads available was never well thought out. For instance, say you requested a log of your Facebook chat logs. Should Facebook provide this without redaction of the recipients' identities? I'd say no, providing this data without that redaction is a violation of the recipients' privacy. Especially for a service that is all about networking and sharing, it's difficult to walk the line between giving the user the data they requested, and respecting the privacy of other users.

The ability to tell Facebook to delete your data does not grant you ownership of that data. You do not have the right to tell Facebook to let some 3rd party to access it using Facebook's infrastructure (which seemed to be the claim made by the original comment I responded to). The fact that the government forces companies to abide by certain regulations does not mean that the company is not the owner of the things that are regulated. A company might have it's interview records audited to investigate discrimination. Does that mean the company does not actually own or possess these interview records?