Note that VOID-in-NULL-out can't be followed blindly. As an obvious-if-you-think-about-it case, LOGIC!-returning routines have to handle void a different way.
Getting Tricked By Inverse LOGIC!
I wanted to write the following;
if exists? maybe some-dir: get-env 'SOME-DIRECTORY [
...
]
If GET-ENV returns null, the MAYBE turns it to void for EXISTS? to process. But...what if the routine were called DOESN'T-EXIST?, and it followed VOID-in, NULL-out? It would make it look like void inputs did exist, if you were just checking the result for truthiness or falseyness. 
This seems like a pretty solid proof that functions returning LOGIC! should not conflate their answers with NULL. (Note: I know exists? is currently conflated with FILETYPE OF, so it doesn't actually return a LOGIC!, but that's just a bug that hasn't been tended to. The point stands.)