The ordinances of the law of Moses were schoolteachers because they provided symbolic precursors to the mission of the Savior. In the vocabulary of the Book of Mormon, these are the "types." Abinadi allows himself this much of an explanation, and no more. We may assume that the theological arguments that explained the practices of the law in terms of their symbolic relation to the revealed Messianic mission were part of the Nephite religion that had been deleted in the Noahite version. Were this brand new information we would expect that Abinadi would at least give a few examples to show what he means. He does not, and so we must presume that his audience understood this argument in depth from the quick reference. This requires that they had heard it before, and Abinadi is simply referring to a known argument.
Apocryphal Literature: See the book of Barnabas as a post-Christian examination of the symbols of the law of Moses, interpreting them in a Christian context, as Abinadi suggests can be done.