I know Intel doesn't support linux on this mainboard. But I hope you support the firmware of the board.
I just had a look into the UEFI Specification 2.4 from Juni 2013. In section 22.214.171.124 is written:
"[..] There may also be an optional vendor subdirectory called BOOT.
This directory contains EFI images that aide in recovery if the boot selections for the software installed on the EFI system partition are ever lost.[..]"
So, a file \EFI\BOOT\BOOTx64.EFI (or BOOTIA32.EFI) is optional. However, the board firmware requires \EFI\BOOT\BOOx64.EFI to be present. Otherwise, it invalidates the BOOTxxxx-entries. In my eyes this is a violation of the EFI standard and a firmware bug.
It looks like Windows (at least Windows 2012) always puts a \EFI\BOOT\BOOTx64.EFI file on the EFI partition and therefore can boot.