Board Thread:Naruto Discussions/@comment-3232093-20140617193601/@comment-28861328-20140818204639

Reread windstar. Marara said that the third eye could only appear in those who have the Rinnegan based on what Black Zetsu wrote on the tablet. Kaguya was no special case, as how else would Zetsu, Kaguya's will, know that.