10.7 Recovery OS used too soon after enabling FiileVault 2

After enabling FileVault 2 in Mac OS X 10.7,
following the prompt to restart,
before the first entry of a passphrase at the EFI loginwindow,
Recovery OS Disk Utility may offer to verify or repair the disk without a prompt to unlock.

In this situation: a report such as the one below should not be read with alarm.

Assume that Core Storage forward conversion of the volume must progress a little, before the volume can become unlockable in the ways that are normal for FileVault 2.

Assume that first entry of a passphrase at the EFI loginwindow will be critical to that progress.

Verifying volume “a”
Checking storage systemChecking volume.
disk1: Scan for Volume Headers
Invalid Volume Header @ 0: incorrect block type
Invalid Volume Header @ 58855587328: invalid field value
disk1 is not a CoreStorage volume
Error: Storage system verify or repair failed.