They have been Granulating powder for around 400 years.
I would think that if shooting just ungranulated powder and fines worked better , they would have stopped wasting time Granulating it.
This is something from the past that has been improver with things like switching to Smokeless powder along with the guns.
But why try to totally Re invent the wheel or build a better Mouse Trap.
I think they tried that with inventing BP subs.
That Works , but not that great. IMO