I dont think it was meant to "fly better" i think it was designed to tear up more flesh on impact.
The rounder buckshot will penetrate easier than a squareish shot.
Being squareish the shot in theory will transfer more energy to the target or BG than standard buck shot.
Just my thoughts on the stuff.
Edit: Did a little research and the OP is right. They can stack a butt load of these things in there.
They may be smaller but i still think that squareish shot will hit with more power than the round shot.
One last edit sorry. Found a pic of the stuff in the shell.
Obviously computer generated but an accurate representation none the less.