From the article's summary of the study, it does not preclude the possibility that the tag was switched on in the children after birth. One would expect that experiencing trauma to the degree of the parents in the study would cause them to raise their children a substantially different environment than they would have otherwise. Since we already know that environment can influence the expression of genes, I don't see why this isn't advanced as, at least, an equally viable theory on why their children expressed similar genes.