Board Thread:Episode Discussions/@comment-25319479-20160526105603/@comment-25122992-20160526181328

There's actually not more evidence for the marking being a SPS result than for it being an MS manifestation. In fact, Hagoromo didn't demonstrate any indications of senjutsu use, we can't even know where he uses it and where he isn't. Also, pretty hard to believe Hagoromo turned on his senjutsu exactly in the moment he awakened the Rinnegan (something he couldn't foresee in any case), so it's surely not the SPS indicator.