Perhaps, that would mean complying with GDPR? You are obliged to remove data physically from databases upon request (including backups if possible, if not possible then keep deletion patches to be ran after backup restore!). Since you cannot continue processing data after GDPR deletion request, that could mean that a model (which is processing the data) should unlearn any knowledge of you.

This is what any reasonable person will think. I fully expect FB to argue that "oh these are just some computer bits you see. There is no way to from this model deduce what inputs made it into this model. It's like a hash function. And since we have removed the inputs, we have complied."

That they are in essence keeping "the ghost" of a person is another thing.

I don't even know if deleting your account through standard Facebook means is the same as requesting the deletion by GDPR request.