1) putting a foot or more worth of absorption material depth behind your screen wall isnt the most practical thing in the world. That said, most of this hobby isnt practical to begin with.
2) safe n sound and acoustic foam are fire retardant, poly batting isnt, so a foot or more depth of it in the theater room is not super appealing.
3) frequencies below 200hz are more easily EQ?d and less directional than those above 200hz, so run your audyssey after all the absorption is in place, and if their is too much gain below 200hz, it will get knocked down.
4) seems like most of us have killer subwoofer setups - if there is going to be a weakpoint in MOST systems (not all), its going to be 80-200hz anyway, so some free gain there isnt the end of the world.
Just my take.