I think the theory is that the field points will be less effected by the movement than the broadheads, so with a bit of adjustment they will come together. If the arrow is leaving the bow a bit askew, the field point will recover faster than a broadhead & hit differently.
If you move the rest towards the field points in slight increments the broadheads should move more than field tips. Often for me the ammount of adjusting needed is very little, less than 1/32" if the bow is close to in tune.
I feel my bow is tuned pretty good if they both hit together & while I'm no expert by any means the things I shoot at in the field usually end up in the freezer.
