So turns out I was too hasty in agreeing with your explanation. The AVS gurus pointed me to these two posts by the Audyssey founder, who has stated that consumer (non-Pro) Audyssey Flat / Music curve has the same MRC dip as the Audyssey / Movie curve. The only way to get rid of it is to use the Pro software, as I have originally stated. (I've updated my post above.)
http://www.avsforum.com/t/795421/off...#post_18910114
http://www.avsforum.com/t/795421/off...#post_19714566