In practice, whether or not this actually works can be very hit-or-miss. We've found several UEFI implementations will not consider a disk bootable if the pMBR doesn't exactly match the spec, which specifies that the 'protective' partition shouldn't be marked as bootable in the MBR partition table.
Meanwhile, other implementations will not consider the disk bootable in BIOS mode if the partition in the pMBR is not marked bootable.
Meanwhile, other implementations will not consider the disk bootable in BIOS mode if the partition in the pMBR is not marked bootable.