That's... a bizarre choice, considering how religious C is about not making any assumptions about what a machine can and cannot do, even going to the trouble of working with non-IEEE floats and int types that are not a multiple of 8 bits.
Runtime pointer arithmetic resulting in a zero-valued pointer, is not a null pointer m, though it is also nonportable and could have the same effect (but hopefully not nasal demons, as I believe this falls under some catagory of nonportable behavior other than “undefined”).
There’s no requirement that the in-memory representation of a null pointer be all-zeroes, only that constant 0 represents a null pointer in source code.
Regardless, I agree that it’s a bizarre choice.
However, to make a pointer to a hardware address at 0x0 in C source code (for either dereferencing or comparison) requires using a special routine, intrinsic, or similar extension so the compiler doesn't track it as a null pointer during static analysis.