Moroni certainly also knows about the parents’ covenant and the oath of defense taken by these young men. Helaman is putting this information on the record as part of the prelude to the miracles that will follow. The contrast between their parentage and their actions makes their deeds even more remarkable. While they were raised Nephite, their parents were converted Lamanites. While the Book of Mormon allows for fluidity in changing political allegiance, it does not change kin groups as easily. The contrast of children of (former) Lamanites fighting valiantly was a useful contrast to the political turmoil of the Nephite king-men who were nominally Nephite but who had refused to fight (Alma 51:13).