What you didn't understand~ is that the comparison from "The Package" was Mark VI..not Mark IV.
They placed "The Package" at a point in the Covenant war MUCH after chief had been out of Mark IV. So either he was wearing Mark IV, and "The Package" was wrong, or he's wearing Mark VI, and, heaven forbid, some movie producer got lazy and screwed up. It's called artistic liscense, and in this case, was used poorly~