Let me see if I'm following what you're saying, Ken.

The shooter should apply the fundamentals of marksmanship even in situations where the enemy cannot be directly seen. You may be aiming at shadows, moving branches or just where you think the sound is coming from but you are aiming at a specific point in space. You can't physically see an enemy occupying that point, but you aim anyway. Correct?

From reading the article it sounds like both the volume and aimed fire schools were missing this point. I wonder what would happen if you tried the different techniques on a target range simulating those conditions, i.e. brush so heavy that you can't physically see the targets but you get indicators like gunfire sounds and movement.