These verses allow Mormon to express his own admiration for Chief Captain Moroni’s defensive wisdom and ingenuity by putting his words in Lamanite mouths. From a purely historical perspective, it would have been extremely difficult for any Nephite to know what was on the Lamanites minds, and these verses are most easily recognized as taking literary license rather than reflecting historical verisimilitude.
The part that the Nephites clearly could see was that the Lamanites had learned from Chief Captain Moroni’s use of defensive armor. The Lamanites copied that armor, with shields, breastplates, and “very thick garments.” See the comments on Alma 43:19 for the Mesoamerican context of this type of defensive armor.