However, Google creates cold backups of "hot data" that last for much longer than deleted data. Depending on the breadth of a warrant, data that was "hot deleted" and removed from servers could still be available on cold backups of the system made before the data was deleted. Unless we have evidence that deletion of hot data implies Google has a method to swiftly and reliably knock out that data in all its cold backups (including offsites).

This is, hypothetically, possible if they encrypt all data on-disk with a per-data-item key and the key itself is never backed up; if deletion deletes the hot key, the cold backups are now just noise and it doesn't matter if Google deletes them.