You do not need a hardware means for the RP2040 to shutdown the SBC.
You can run on the N100 a program that would monitor continuously the RP2040, e.g. by reading periodically the state of a GPIO pin or of a variable in the internal memory. Such a program can shutdown all the SBC.
I suppose the usecase would be a "poor man's IPMI", a separate chip dedicated to monitoring the main system, with the ability to power if off and on.
Sadly most(?) x86 systems don't offer a non-visual way to access BIOS/UEFI settings (like ARM boards usually do with uBoot over serial), so the utility of such monitoring without video input is limited, but just being able to remotely reset a system via a built-in chip would be very useful.
You can run on the N100 a program that would monitor continuously the RP2040, e.g. by reading periodically the state of a GPIO pin or of a variable in the internal memory. Such a program can shutdown all the SBC.