Somehow I missed commenting on this earlier. Very interesting demonstration. One huge difference between the two rooms that might go un-noticed is room volume. The 'reverb room' could be a gymnasium with a high ceiling, while the anechoic chamber may only have the volume of a small bedroom.
One of the major, reoccurring acoustical problems in both residential and some commercial rooms are due to over volume, thus becoming 'echo chambers'. Fixing this after-the-fact is often problematic...and expensive.
