Castings are somewhat a black art, the practical tolerances are large so yes you will get some castings that will be machined out into fresh air in sections when bored for 920 and others that show no signs. With such large variations the other black art was where to take the first datum cut so the subsequent cuts did not scrap the casting. All while the buyer was telling the casting maker they were casting them too heavy and the price was too high and to save some weight and cost.