One photo never tells the story.
Actually, the back side of the TV is covered with two inch sonex. This is "even better than nothing," in the sense that the sonex is better than just air.
If you look closely at the photo, there is a six inch steel I-beam right behind the TV, floor to ceiling that helps to hold up the ceiling, and the seven foot grand piano that is directly above this room.
There is about four feet between the I-beam and the rear wall, and that's where the subwoofer is located. It is oriented vertically, which gives measurably smoother response from 25Hz to 40Hz.