When we think about layers in photography, we think about planes. What exactly is happening in the background and foreground? There's a third layer also: the interplay occurring between those two grounds. That tends to provide directionality, be it narratively or visually—pg. 33, the foreground (family) and background (house) establish the setting but it's the little boy in the lower half of the frame that is the subject, the one who rounds out the image and hands curiosity a dagger.
But layers alone wouldn't make Webb's photos so emphatic and loud. When I look at an Alex Webb photobook, I think about every which way I would have missed the shot. I think about the fact that there are about 3-4 ways I could have framed it and thought "Yeah, this is great." Or the various ways I would have cropped it afterwards and said "that's it, man!" But then, the photo would only exist as a fancy ornament, not an artistic documentation of repression, death, and community. The full frame gives you the full picture (pun intended).