Plywood has higher absorption than sheetrock or hardwood, but we should remember that Ron speakers are dipoles with 100% back radiation. When using the Soundlab's I have to partially absorb the back radiation, but for the XLF's I need a more reflective front wall. I also prefer livelier rooms - IMHO most listening rooms are too absorptive.
Bonnie likes plywood precisely because it has higher absorption than drywall, which actually is quite reflective. I wrote Bonnie today that I am open to her programming in hardwood walnut (which would match the speaker/amplifier wood floor section of the listening room anyway).
I do not want to debate here absorbing versus diffusing the back wave of dipoles. (We have discussed that elsewhere.) I believe in doing neither, so my front wall will be 5/8" drywall over 2" of firred-out wood framing filled with blue jeans insulation.) I try to encourage an unadulterated back wave reflection off the front wall.
I think people often over-damp their rooms too, but I always really like how a quiet room "sounds."