One of the questions to be asked of the book of Ether is how Moroni used Mosiah’s translation to create his text. The plausible answer is that Moroni followed his father’s practice of using the plates of Nephi. There would be times when Mormon recounted the story, and there were times when he copied information from his sources. Moroni appears to be using that same method.
The difference in detail between the recounting of the Jaredite preparations to embark on their journey to the New World, that precede and follow the insertion found in verses 7–12, strongly suggest that Moroni is retelling the story at this point rather than copying it.
A second question might have been whether it was Ether or Moroni who made this insertion into the story. These two verses strongly suggest that it was Moroni. Both he and his father address the future Gentiles, for they knew that they were writing (at least in part) to them. Thus, verse 11 should be easily assigned to Moroni; therefore, the rest of the verses, by association, should be assigned to Moroni as well.