For some reason (probably due to QEMU), these kinds of bootloader tutorials are still stuck in the BIOS era. UEFI remains completely under-taught, which is probably in part because it's hideously complex.

Note that modern computers are supposed to be dropping BIOS boot support this year[1].

[1] https://arstechnica.com/gadgets/2017/11/intel-to-kill-off-th...