In this case, I would say that backups are not relevant protection. In order to restore something from backup, you would first need to know that a restore from

In this case, I would say that backups are not relevant protection. In order to restore something from backup, you would first need to know that a restore from backup is needed, and secondly you need to know what the last-known good copy is. This is a silent data corruption bug (data is written at the wrong offset, IIUC) with no known method to detect the error condition except to compare the resulting data with a known-good copy. The next backup run will happily accept the corrupted file contents into the backup vault, and unless someone happens to stumble upon the corrupted data, the last-known good copy will eventually be rotated out.