Moreover: if this (i.e.: DBA) was truly about physics and adhering to that, it’s conspicuous that the sheer size and displacement area of subs isn’t taken more into consideration.Uh... it is.
The size of the subs *has* been taken into consideration by Duke of Audiokinesis and that is the beauty of his system. His subs are 1 foot square by 2 feet (using a 10" driver), which is fairly small as subs go, yet they go flat to 20Hz. He gets away with that because they are designed to work in the room boundary effect and so roll off at 3dB/octave starting around 100Hz. This means they have to be placed close to the walls (which usually happen to be more out of the way, resulting in inconspicuous placement in most rooms) in order to work right. It sounds to me from your comment above that you might have missed this bit in the prior conversation. Most subs are not designed to take advantage of the room boundary effect because the right place to put them is likely not against the wall- its where-ever in the room it has to be in order to work.