User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-74.12.2.113-20111217202326/@comment-76.69.7.125-20111217230052

From what I know, download quests only contain the quest data. The monsters, items, and equipment are all in the game's data already. The 3DS is capable of DLC (hell, one of the built-in games just got a huge update) but then Capcom would have to work on more monsters.

It's similar to Dragon Quest IX, which had "downloadable quests" which were built-in to the game already and downloaded absolutely nothng. Going online simply enabled them.