The thought was just to avoid dependance on the apple pc-bios emulation and go toward a grub.efi installation as you suggest. (Also the apple Xserve machines do not have pc-bios emulation.)
In both these cases the blessed grub.efi file is selected and boots.
The boot.efi file here is a copy of the OSX boot.efi
im81:~ pxw$ bless --info /Volumes/hfsp
finderinfo[0]: 7891 => Blessed System Folder is <missing>
finderinfo[1]: 8123 => Blessed System File is /Volumes/hfsp/efi/test/grub523.efi
im81:~ pxw$ bless --info /Volumes/hfsp
finderinfo[0]: 8120 => Blessed System Folder is /Volumes/hfsp/efi/test
finderinfo[1]: 8123 => Blessed System File is /Volumes/hfsp/efi/test/grub523.efi
im81:~ pxw$ ls /Volumes/hfsp/efi/test/*.efi
/Volumes/hfsp/efi/test/boot.efi
/Volumes/hfsp/efi/test/grub523.efi