boot1.efifat's FAT12 volume label prevents booting (some systems)

[Harry Schmalzbauer]

 Recently I played with bsdinstall and UEFI setup, which left the system
unbootable (11.0-Release).
The culprit is the MS-DOS volume lable "EFI        " of the EFI partition.
At least on Intel Single-Socket Servers (for Xeon E3 IvyBridge/BearToot
+ Haswell/RainbowPass), the UEFI firmware can't handle the identical
path/volumelabel.

Simply reformatting with a different volume label (EFIFAT e.g.) solves
that problem!
Shall I file a bug report?

Btw, can someone explain in short words why BOOT64.EFI seems to be
boot1.efi, but padded with 0x20 up to 128k?

Thanks,

-Harry