I wouldn't be so sure. As a developer I've used a similar strategy to make restoring important data easier that occasionally would be deleted by mistake. This wasn't private information though.

Also, I have zero confidence that any of the big tech companies thoroughly delete data they've obtained even if it's illegal to keep. Big tech companies aren't exactly known for following the law. While GDPR sounds nice in theory, the U.S. based companies might "delete" the data from E.U. servers, but conveniently keep backups in the U.S. Or they might forget to pass on the delete request to trusted third-parties.