I’ve updated the FileVault 2 status check scripts so that they’re now able to correctly handle unencrypted Fusion drives. The scripts should now report accurately on 10.8.x Macs that use Fusion drives, as well as other 10.7.x and 10.8.x Macs.
The changes are now available as part of my regular script. They have also been rolled into both the Casper Extension Attribute and the Absolute Manage Custom Info Item scripts. Use them in good health and please let me know if you find any problems with them.