Help with decking or not?

I've seen many 440's torn done for the first time to be bored and other basic machine work. They find out the replacement piston are a lot lighter than what they had originally and needs to be rebalance. Only to find out that the stock piston were 20-30 grams different on most of them and the crank wasn't balanced that closely either. But other than that, the engine ran great with no noticeable vibrations or issues you would expect with that much of a mismatch from the factory.