Board Thread:General Discussion/@comment-3542839-20140227002012/@comment-30269377-20140605004052

Well, see, in the earlier twists you mentioned, the information "twisted" is revealed to the heroes to be true, or the heroes just believe that it means something that isn't true. However, in the 7 heroes of Olympus part, he literally writes to the reader, Annabeth is the seventh hero. Therefore, there can be no misconception, nor can it be false as the information is disclosed to the reader directly.