>  i.e. repeating anything i can see from the code (like “returns void”) tells me nothing.

It's right up there with using #defines for silly things like
    #define FOUR 4

Great.   What doe this tell me that the literal 4 doesn't.    It's a matter of time until someone says
    #define FOUR 5

I actually found some code in use that had

#define notdef 1

in it.    I about went through the roof.

Frankly, I have immense distaste for the definition NULL.    Especially those implementations that try to fix it by introducing a spurious cast on it.