Mac EFI login [Update Needed] - FileVault

I use Disk Utility > Erase > Mac extended (journaled, encrypted)... to prepare my internal boot drive. This means I get two logins: EFI disk login and OS user login. When I restart after installing Sierra, the EFI login shows a question mark icon with my name replaced by [Update Needed]. Apple Stack Exchange shows an identical 2012 photo here. Google shows same issue through OS X and into macOS. Flash is blamed, but that line of enquiry got me nowhere. Terminal commands enable auto login (that incidentally failed on my Mac Pro, see OS X: How to disable automatic login when FileVault is enabled). After running those Terminal commands, I noticed an apparent bail-out in System Preferences > Security & Privacy > FileVault.

'Some users are not able to unlock the disk. Enable Users...

Click the lock to make changes.' -- I remember seeing that in El Capitan, without that [Update Needed] that appeared with Sierra.

Has anyone else using FileVault found similar issue in macOS Sierra?