I agree, they get mashed up oh so often, but the point of OUaT is that they attempt to show us how this might have happened and how the stories connect in a logical way.
In quite an innovative approach, they try to make those fairy tales HAVE SENSE. If we approached all the clues they give us with “they are just all mashed up and they can’t possibly make any sense” attitude, it would be no fun! 😉