Cannot erase a Filevault encrypted disk with Disk Utility app from 10.8

Running a 2012 MacBook Air with it's factory image (10.7.4) installed and Filevault encrypted.

I need to erase this disk to drop a new image to it and am leaving the disk locked on purpose. The disk is locked to emulate the need to erase and reimage machines returned to me that are still encrypted with an exited/terminated user's data still on them. I could input the key, however in the interest of time or other factors, it would be far easier to issue an erase to the disk and then proceed immediately with an image deployment.

I am booting from a disk with a 10.8 OS image installed on it or a USB with the 10.8 install (InstallESD), and I'm running Disk Utility from either of those disks. When launching Disk Utility, I am prompted for a password to unlock the volume. I cancel and proceed to attempt to erase the disk. This is not possible, as the Erase option (when clicked on the disk and not the Partition) is completely gone/unavailable. This was not an issue with 10.7's Disk Utility, and have been able to reproduce this issue on other machines. 10.7's Disk Utility can erase the disk, however 10.8's Disk Utility cannot as the option is gone.

Is this a known issue or a change to Disk Utility's GUI functionality? This presents a problem to enterprise environments where obtaining/inputting a key to unlock the disk (only so it can be erased) could be considered a waste of time, or where we may not have a way to unlock the disk for one reason or another. Some environments still rely on Disk Utility's GUI interface for imaging machines and therefore this is a problem.

I checked running diskutil to see if I could issue an eraseDisk and was successful in doing so, so it appears to be a GUI only issue. e.g. "disktutil eraseDisk JHFS+ testname disk0" works fine and erases the encrypted disk. This leads me to believe there is either a bug in Disk Utility on 10.8, or that the functionality was pulled on purpose.