In the schematic on Radxas site[1] there is no connection between the RP2040 and the power circuit, I would love to be able to shutdown the Intel chip from the Raspberry Pi microchip. Seems far fetched that it would be hackable if this is not a feature, I'm guessing the power chips are a lot more complicated and undocumented than a RP2040.
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.
[1] page 22 https://dl.radxa.com/x/x4/radxa_x4_v1.11_schematic.pdf