In active full backups, the entire dataset is backed up each time the backup job runs, whereas in synthetic full backups, only the changes since the last full backup are backed up. If the engineer configured the backup job to run active full backups instead of synthetic full backups, it's possible that the data from the full backup taken 60 days ago is still being retained as part of the regular backup process. Therefore, it hasn't been removed automatically after 60 days as expected.