The small drill hole is called the vent hole. It allows air and sizing lube to escape during the sizing process. If it was not present, the cases would most likely have marks that are called lube dents. The mark is cosmetic only and presents no safety or functional issues.
When you lube the case for sizing you need only lube the case from the shoulder down to the ejector groove and inside the case neck. Do not lube the case shoulder or the outside of the case neck.
