Think about it like this: micrometers get into the tenths. You are talking about adjusting the opening in tenths or thousandths for a powder that is bigger than that, and how the are arranged in the internal funnel will ultimately determine the final load you get. Spherical powders May offer better results., but you will still end up crunching some. But if you are only looking to use it to mark where you need to be for a certain powder then it may prove useful as long as you have a bunch of one powder or your choice of powder has lot to lot consistency.
You could probably get just as close with a dial caliper by measuring the screw stick out when you hit your desired load. Record it and move on.