A wonderful conundrum!
Punching out those holes caused wear and tear on the tooling. So why continue if there was no need? Except that it was a one-year problem.
Euclid, I think, posited that "three points determine a plane". Maybe those, and something at the top of the shell (the hole that the emblem used?) located the shell for the molding of the shell and other activities.
But then there are the offsets for the hood. Were they done after the grill was formed? Probably. They didn't have to look too good because they would be covered.
And why none on the commercial hoods?