How hard do you think it is for the dev's to move the invisible barriers? Moving Barriers is simple repositioning them all just takes time and cannot be done in one go. But it can be done by one department unlike making a 4 man dungeon which requires more then one department being involved. There is a big difference between them having time to make totally new content and having the time to go back an make changes to existing content. There is also the fact the various departments that make up the dev team dont all have free same at the exact same moment. Moving the barriers is also one change that even Yoshi would most likely not notice.