Snapshots are deleted after point-in-time rollbacks
In the case of the VSO FIM snapshot method for Network Attached Storage (NAS), when you perform a point-in-time rollback from an older copy, the snapshots on the storage array after that point are deleted. This operation renders the NetBackup image inconsistent, thus the image is deleted.
Similarly, when you perform a point-in-time rollback of an older snapshot from one of the mountpoints, only the snapshot that is associated with that mount point is deleted. Also, the images are deleted because they become inconsistent. However, the other snapshots belonging to other mountpoints would still reside on the storage array and you need to manually clean them up.