Blaze im gonna prove you wrong right now, its page 9 of chapter 386 where itachi states that "the transplant for the EMS gave birth to a completely new doujutsu" hes only like he said telling you half of the story that he knows, when you said that doujutsu was the rinnegan its was obvious that you were correct but however, i don't think you were completely reading everything it said, because if you go back to that chapter and read that page over again itachi says after he tells sasuke "That the transplant gave birth to a completely new doujutsu(the rinnegan)"than he says that obviously this exchange could only be done between clansman" than after that he says(and this is the part you missed) "AND SIMPLY GAINING ANOTHER'S EYE'S DIDN'T EQUATE TO GAINING THIS POWER" hes talking about this new doujutsu aka the "rinnegan"basically what itachi is saying that only because you obtained the ems by adding another clansmans mangekyou sharingan(their eyes), that alone is not enough to acquire the "new doujutsu" which like you said is obviously the rinnegan, sooo.. what other stipulation can their be? of course its senju dna.