Hmmm - Well, the first real mod I did to my Impreza was to swap out the drum brakes for a set of discs taken from a Legacy wagon. The improvement in braking feel was pretty tremendous, and the overall stopping power seemed to go up as well. I would not want to trade back to the drums under any circumstances - I hated everything about them, quite frankly.
I can't say anything technical to discount your theory, but my personal experience with the swap was quite different from what you're suggesting. It's possible Subaru doesn't use any of the special tricks you mentioned with their drum brakes, which would explain why they felt so awful to me and why the discs worked well.