Some minimal tombstone metadata like “This ID was a post/image” is kept around for things like error messages (“The post you are trying to view is not available. It may have been deleted or you may not have permission to view it.”). There might be exceptions for illegal things (like child pornography) where there’s some obligation to keep the data (or a hash or something) for law enforcement purposes, but I’m not aware of any.
You can try to argue that the author wants to keep things simple for a general audience. Though a cynic would point out that one of the authors is FB's deputy general counsel, the type of person who we would expect to be incredibly precise and purposeful about wording.
I looked around on the FB support pages for more clarification and this is the best I could find:
https://www.facebook.com/help/224562897555674/
> When you delete your account, people won't be able to see it on Facebook. It may take up to 90 days from the beginning of the deletion process to delete all of the things you've posted, like your photos, status updates or other data stored in backup systems. While we are deleting this information, it is inaccessible to other people using Facebook.
Since it is talking about deleting backup/caches, I think it's reasonable to interpret that they mean a complete wipeout. Though I assume there's no guarantee either -- i.e. if FB's deletion process "happens" to not wipe out the cache or do a real wipe, how can we really confirm?
For a non-Facebook example, here's how Google talks about deletion of search activity:
https://support.google.com/accounts/answer/465
It explains that Google will retain the "meta" of your activity, and also says that the meta will be removed if you delete your account:
"When you use Google products and services, we keep some data with your Google Account, like when and how you use certain features. We keep this data even if you delete activity or other items. For example, if you go to My Activity and delete a search you did on Google, we'll still know that you did a search, but not what you searched for. What you searched for will no longer be stored with your account...We keep this data as long as it's relevant to meet uses like those above. If you delete your account, we remove this data from it."
How could this even be enforced? If something like the GDPR gave you the ability to request that your data be deleted, would that extend to learned data?
In my opinion, there's no way they could make FB delete that kind of data. How would you even know they had it? It's not like FB would throw out entire trained models or attempt to retrain with everyone else's data, that would never make economic sense.
Could someone with more knowledge of the current data protection laws comment about how|if this is addressed? To me it seems like companies could just process all your data into some derivative and then delete the original data to stay compliant.
I'm still not absolutely certain it is deleted from disk.
If it is recoverable, then it falls into the ominous term: Pseudonymous : https://www.wsgrdataadvisor.com/2015/09/personal-data-anonym...
If it's a) then that's either a 'hidden' toggle which does not meet GDPR needs. If it's a 'hidden' and do not process further, it is questionable (unless a right to be forgotten is invoked).
Also if it's a) then everything is discoverable by someone with legal authority, even years after you believe you have deleted it.