iMac M1 24" teardown

Reading it, I noticed one thing that maybe someone else here might better understand.

In step 8, they show 64MB of NOR flash memory in addition to the 256 GB of NAND flash. Looking back at some older teardowns, it seems that the earlier M1-based Macs also have it. I wonder what this is for.

On a more traditional microcontroller this is usually memory-mapped to CPU address space and contains the embedded application, with any “external” flash being used for a file system. On a computer-like environment, it would contain a BIOS-like firmware (e.g. the BootROM code on Intel Macs or the OpenFirmware of PowerPC Macs).

I wonder if Apple is using a separate chip for the ISC APFS container that contains the M1 equivalent of BootROM code. If so, that would be a great idea, since it would mean hitting the wear limit on the NAND flash wouldn’t destroy the computer’s ability to boot from an external SSD.

Is anyone here familiar enough with these new computers to know what that separate 64M of flash storage is for?