Any Active Directory backup is always a NetBackup full backup, whether it is a granular backup or not.

Whenever Active Directory is in a policy's Backup Selections list, the Active Directory portion is always fully backed up, even when the backup type is incremental, differential or cumulative. Any other items in the Backup Selections list may use a differential or cumulative incremental backup type as indicated. Even though a full backup is forced for an Active Directory backup, normal incremental rules are applied to the non-Active Directory items in the policy file list.