If you are loading for an AR then you will need to Full Length Resize every round. If you have full length sized the round, there is no need to neck size, the case, and mouth have been sized. It is a wasted step as far as I know.
I shoot a bolt action. I neck size for the one, and only rifle the loads will be shot out of. I load a few to shoot out of AR rifles that belong to friends. I Full length resize for those. They shoot more accurately than we can milk them for.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.