[mjg59]

Former google employee, no knowledge of current situation, not involved in any of this stuff even when I worked there: different types of data get handled differently. If material is important enough then it's going to be backed up onto tape for disaster recovery purposes. If a user then requests it be deleted, that's a huge pain - the easiest thing to do is just wait until that tape has rotated out of backup, which may take a while.

More sensitive user data is likely to be handled differently - both for privacy reasons and because it's honestly just not as important to keep hold of it (a user's cloud data gets lost? That's a big deal. A user's location history data gets lost? Meh), so it's unlikely to end up in long-term backup storage.