The picture comparing the Fox to the Elsie illustrates a large portion of the problem. There are many factors which contribute to the cracking problem but removing that much material certainly weakened the overall strength of the head which allowed stress to be relieved. If there is stress to be relieved the receiver is unyielding so it is the stock is what has to give.
Many examples have been subjected to incredible amounts of abuse and remained sound so the problem is not universal but if the stock blank was deficient in quality or curing the cracks are the result. The good news is that once that stress has been relieved, judiciously applied epoxy probably makes them even stronger than new.