Mormon continues the list of things that were preached. Among the preaching against lyings and deceivings, there is also the very important teaching about the “coming of the Son of God.”
All of these things simply establish the ending of the story of Alma and Amulek’s preaching tour. Mormon has left specifics, and is simply noting that outside of Ammonihah, good was accomplished. Putting an end to that story allows him to return to Alma’s personal record and the next important story he wanted to take from that record. That begins in the next chapter.
This chapter remained unchanged from the 1830 edition, when the 1879 changes to the chapters were made.