The six-part structure of ancient Hittite treaties, also found in the Bible, was only noted and studied in the 1900s, making it unlikely that Joseph Smith could have known of this or consciously imitated it. Osmosis, luck, and bad LDS apologetics are alternate explanations. But the understanding of ancient covenants is important for an issue of more general interest: the Bible and its origins.
In the debates over the origins of the Bible, a large number of modern scholars have found it fashionable to view the early books of the Bible as late fabrications largely composed after the Exile. The details of Moses and the Sinai covenant, for example, are often presented as a late evolutionary development not grounded in history. However, the presence of such ancient treaty structures, significantly different from known treaty structures in the Near East after the Exile, suggests that the accounts in the Bible have much more ancient roots.
The similarity of the form of the "Hittite" type of treaty with the structure of Exodus 24-Leviticus, Deuteronomy, and Joshua 24 directly bears on the question of the dating of these narratives. Many scholars acknowledge the antiquity of these biblical treaty-texts because of the similar structure of the six points of the Hittite treaties. Mendenhall, for example, concluded: "It is very difficult to escape the conclusion that this narrative rests upon traditions which go back to the period when the treaty form was still living." Klaus Baltzer maintained that "it remains, however, a striking and historically unexplained explained fact that the Old Testament texts resemble most closely the highly developed formulary of the Hittite treaties." Kitchen determined that "if we take the nature and order of nearly all the elements in the Old Testament Sinai covenant and its renewals [i.e., Deuteronomy and Joshua 24] ... it is strikingly evident that the Sinai covenant and its renewals must be classed with the late-second-millennium covenants."
Source: James K. Hoffmeier, Ancient Israel in Sinai: The Evidence for the Authenticity of the Wilderness Tradition (Oxford: Oxford University Press, 2005), Kindle edition, chapter 8, section IV, "Ancient Near Eastern Treaties and the Sinai Legislation."Hoffmeir goes on to review the attempts of some scholars to dress the Biblical covenant material with much later robes, but the fit is rather poor.
My first introduction to these ancient covenant patterns came while reading Jon Levenson's marvlous book, Sinai and Zion. This aspect of ancient covenants deserves more attention for better appreciating the Old Testament as well as LDS material.