Does the user_backup_pre.sh script (http://help.directadmin.com/item.php?id=287) also work when creating backups via 'Admin Backup/Transfer' in admin level or only when creating them via 'Manage User Backups' in reseller level?
It will be called for backup creation at all 3 Levels:
Admin Level -> Admin Backup/Transfer
Reseller Level -> Manage User backups
User Level -> Site Backup
all 3 levels create the same tar.gz file (with varying names), and all 3 will call the script.
Note, we have found a bug where the data isn't cleaned up if the user is skipped via non-zero exit (/home/admin/admin_backups/username/backup, etc..). It's fixed in the code for the next release.