What about data that Facebook generates about you, but you did not provide? Is that information required by the GDPR to be provided to you, or does the GDPR only state that any information you provided to them must be returned? There's no way I'm reading the GDPR nor would I even understand all of it if I did.

We know that FB makes connections between you and other users even if you've never made those connections yourself. We've heard about the shadow profiles, etc. These are all data points that FB generated on their own. It seems like this is the information that is valuable. Information gleaned from ML analysis of images posted would also be their own. That has way more value than the image itself would. FB is doing way more under the hood than just slurping in the data users posted, and then displaying it back to them.