The war-Noir relationship strikes me as roughly comparable to the Depression-horror one. There appears to be a connection and yet it isn't stated. Like Noir, horror continued well after the era that spawned it, so to speak.
If not, I think there's much more to explore.
So I'm not sure I can fully ascribe to your theory, but then again I am prone to view noir more as style than simply genre, style that can and often does encompass several genres. It's a very interesting topic, however, always ripe for discussion, and your thoughts are intriguing and well-thought out.