Somebody who asked to remain nameless told me that when he was working up a truly awe-inspiring pistol cartridge once upon a time, that he could get Unique to act like BE, and 2400 to act like Unique, by compressing them strongly. Apparently BE, Unique, and 2400 should never be compressed. I would suspect that to be a more general rule about flake powders than something peculiarly specific to those three. Flake powders are the most extreme conformation geometrically, so more liable to get their burn pattern modified by compressing.
That said, I am a huge fan of BE, Unique, and 2400.