I would like to think it's intended. Baking cornbread (or similar breads) in a mason jar is actually real life. Bake it, seal, shelf stable for some time. So, it make sense.
They do it for several foods that required a jar of water to cook. I assume they do it to simulate not losing the jar when cooking the food, but when you loot that food or eat it way after cooking it, it just seems odd to magically get a jar back from it.
