Kirk - Sorry if I offended you. Wasn't meant that way. I am sure your source has had plenty of experieced with MLs. But, as with all gun writers, not everything they say is etched in stone.
Personnally, as had a lot of other guys in this forum, Ihave worked up loads for many a ML. And I have yet to find a GM or T/C barrel that was in good condition that I could not get to shoot well, if not exceptional.
I'm glad you found your rifle's sweet spot and wish you liuck on your future hunts.
ps: Like dave said - the corn meal or wad acts as a cushion protecting the base of the bullet and helping to prevent gas blow by for more consistant pressure - hence better accuracy.