[bigyabai]

It's Apple's bootloader. They were the ones that chose to use iBoot and not implement UEFI-style booting like prior Macs.

[throawayonthe]

...why would they, this is a strict improvement with less surface area

[bigyabai]

Because it was a featureset they supported without trouble on prior Macs?

The onus is on Apple to not make iBoot suck, they don't get a free pass for Microsoft-level boot volume ignorance.