Those happen to be 61/05 but that doesn't mean anything. I've got other crates of 61/05 with virtually no cracks, too. And I've looked a bit more now and there are cracked ones with 61/08 and 61/07 too. You may not have any, or you may not have noticed them since they are not that apparent until you look for cracks, but the cracks are in most of the batches to some degree. Some crates have almost none, others have quite a few. I go through far more ammo than most, so I've seen the good, bad and ugly.
But why I actually got involved in this was because someone said they had seen cracks in the
head of the case, and I have not seen that. Cracks in the head would actually concern me. Necks- not so much.