Well, I'm not a headphone engineer, so I can't tell if they are just wired to double mono or if they are regular stereo with the front signal panned in the middle to make it sound as it came from 12, or if they have some electric circuit to do the panning. Nevertheless, as long as we don't have a third ear in the middle of our foreheads, it's impossible to make headphones with a single front centre speaker element. I guess the multiple element design works best with your diagram to make a difference between front and back, the centre thing being more like in the movies reproducing mostly the dialogue. In fact, I think the helmet thing in the beginning would beat all headphones measured by the veracity of the 3D experience.