I agree with you, I dont see a difference between moonlit, brainstorm, or crimethink. They all grant players access to walk on the walls, hoever, DT didn't want people to get on the walls in moonlit because he never INTENDED it to happen. He said he had the map thoroughly beta tested and no one ever discovered it...
Do I personally think this makes sense? No not really, but his major point behind barring it on moonlit was that wall walking was never inteded.
<3
Gibb