On ARM it does, as I mentioned in the article (though it isn't directly useful to us, as it's too different from Linux ones).
But yeah, assuming there will be no Intel machines in Apple's line-up at some point in the future, I wouldn't be surprised if they drop out of the Forum.
They even use device tree on x86 too (in addition to ACPI/EFI). The plaintext password and user guid is passed in chosen fields for instance when boot.efi unlocks an FDE disk.
But yeah, assuming there will be no Intel machines in Apple's line-up at some point in the future, I wouldn't be surprised if they drop out of the Forum.