The EFI jumpstart is particularly clever. A straightforward recipe for locating and verifying the file system driver, and then once executed the UEFI pre-boot environment can fully navigate an APFS volume.
Uhhh, personally I'd prefer that UEFI stay away from the OS particulars. But anyway, afaik Windows' boot code had about the same feature―at least it certainly did in regard to the chipset drivers, the result being IIRC that the OS wouldn't boot if you moved the partitions a bit.
The pre-boot environment needs to find the kernel and initramfs somehow. My guess for how Apple is booting from APFS, now that it's all APFS, without a separate recovery partition? They've got this minimalist EFI jumpstart code in the firmware, it loads the EFI file system driver for APFS, and now it can locate the bootloader, kernel, and kext cache.
For a long time Apple has had an HFS+ driver baked into the firmware. The way APFS is implemented with EFI jumpstart, they've got much less filesystem code in firmware.