All Treasure Structures generating in Overworld preset

When you generate a new world with preset "Overworld" you get all the treasure structures, such as pirate ships, pyramids, igloos, ocean ruins, witch huts and temples. I have included some pics to show you. I been playing the snap shots and have not seen this before, but as i have not generated a "new world" in a snapshot for awhile it possible this is and old issue.