Ya I agree, Ive see that alot as well. Here are some interesting #'s.
All #s are based on , FRONT, CENTER, RIGHT, SUR RIGHT, SUR LEFT, SUB respectively:
Avia disc (using and oppo dvd)the calibration is 0,0,0,3,4,-2(reading from 990 menu)This was also read in the menu @0 volume, the db with the SPL meter was 85, 80, 85, 77, 77, 85. you can see that the fronts were normailized at 85db and everything else was too low illustrating that using a Avia disc may be correct when playing the Avis disc(who knows about other DVDs)but is not accurate for anything other than the dvd input into the 990.

Here are the #'s for manual 990 calibration using a SPL meter with 0 volume and calibrating to 85 db.
0, 5, 0 ,11, 12, -2.
My speakers are a set of B&W 602s3(7" woof)B7WLcr60 s3(2x 5 1/2 woof), B&W M1 for surrounds(4" woof)and B7W 650 10" sub.
It seems that the 990 Maunual caibration makes sense with boosting the center(not sure if 5 points is right)but needing more volume for the rears maks sense.
Anyways take a look and comment if you have any insight.
rob