Could be that their audio playback is done by hardware reading from a low address buffer in parallel to the rest of the logic and just relies on that logic to update pointers otherwise it will run through the entire address space.
Or it could be their way of implementing a full address space dump on a crash without large amounts of storage available and that just includes the ROM because it's a part of that address space. But in the video, they were able to get a 100% match for the ROM using an emulator, so this isn't it unless they didn't mention chopping off a RAM section.
Microsoft is looking for it and it wouldn't surprise me if they are paying a decent penny for it to try to stop the Linux gaming momentum the deck is driving.
It's entirely irrelevant to me. I don't care what the specs are if it's just running Windows.