Board Thread:Theories and Speculation/@comment-28939725-20161201164545/@comment-25122992-20161204204409

It's just an assumptions. He didn't use other paths in the series, so he isn't their user by default, but it's almost the same case with Madara/Sasuke who even were the orinal owners of their Rinnegans, yet haven't used most of the techniques Nagato demonstrated. But I think it's the right choice, since it'd be quite boring to see the same techniques again and again.