Again, in parallel to the sons of Mosiah, Nephi and Lehi enter the Lamanite lands and are imprisoned (as were three of Mosiah’s sons in the land of Middoni). As were those sons of Mosiah, Nephi and Lehi are not treated well in prison.
Secular records from the Maya suggest that the mistreatment of captives was common and to be expected. Of course, that might also be said of so many other ancient cultures that even though it fits in that context, it isn’t exclusive to that time and place.