> To boot from a CD-ROM or DVD-ROM in the boot services environment, an EFI System partition is stored in a “no emulation” mode as defined by the “El Torito” specification.
This was chosen specifically to allow polyglot ISO files that can both be booted bh UEFI and legacy BIOS. The implementation of tools to create such polyglot files are, to say the least, interesting. The tools effectively generate both a FAT and ISO partition, each having its own file information table, but sharing the actual file contents.