If we had to scrap all of the engine parts that were torn down and got some scratches on the deck faces, it would get very costly... So you run them fat so there is meat on there to do a skim mill on those faces to clean them up and make them good again... You run them to the high side of the tolerance spec so you can mill them and be in the middle or low end of the spec and still be usable...
They are only allowed to vary 1 compression point in production... If they run more than one compression point for variation it is a federal emissions violation which can lead to a recall and re-certification if caught...
