While I have no way of knowing why or if Cody might prefer a messenger bag/haversack over a backpack, there are perhaps some advantages for his style of survival.

For example a messenger bag/haversack and be adjusted quickly to ride more on the back, side or front depending upon how you want to distribute the weight. It can be accessed without having to remove it from your back. If one is foraging, you can pull the bag to the front and place or remove what you want inside quickly. It can be moved from one shoulder to the other easily. It can be carried in a tumpline fashion.

The versatile nature of how a messenger bag/haversack can be carried makes me think that it would make a good choice for a minimalist survival style such as Cody’s.

Pete