Can you explain exactly how the LU policy (ru6) is best configured ?
Enable the delta files download from LU server with [LU settings policy] > Windows Settings/Advanced Settings > Let clients download smaller packages from a LU server
Of course this only works if LU server download is enabled.
Notifications for full downloads can be created under Monitors > Notifications > Notification Conditions > Add ... > Network Load Alert: requests for full definitions
Unfortunately, in 12.1.6 all full definitions are triggering alerts while only AV/AS definitions are critical for bandwidth.