"Rotate fronts side to side keeping wheels in same position with moving tires side to side so rotation stays the same about every 15k. Leave rears alone."
Do you mean the rotation direction of the tires?
Most all tire treads feather to some extent, front or rear, and rotating to the opposite side of the vehicle changes the tire rotation direction and smooths out the feathering of the tread (and then it begins to Feather the other direction).
Agree on a dually, leave rears alone or maybe swap them side to side once or twice depending on tire life to correct the feathering on the tread, but certainly not as important as fronts or srws with less rubber on the ground.