Quite by accident, I ran across this same problem, and a LOT of Googling randomly had me stumble across a solution from this link:
http://forums.macrumors.com/showpost.php?p=14087907&postcount=225
I have no idea where this syntax difference is documented, what it means, how it works, or why, but it did work for me. I hope it's useful to you as well. I would love to know if anyone can explain why the EFI Shell (or at least certain versions of it) have this ridiculous, seemingly undocumented quirk.
-- Gwynne Raskind