Ok, well. Blizzard disagrees with you obviously. You're trying to make sense of lore that was never 100% consistent anyways. People here are giving reasons that make sense but you just disagree with them. So, whats the point exactly? What are you trying to prove? That Blizzard are bad writers? That ain't news.
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Arbiter just makes the decision. Kyrians are the one who ferry them. The Oribos cinematic and the way the place looks aesthetically with the souls going to and from the Arbiter doesn't make much sense. Unless the Kyrians just leave the souls in a certain place which we haven't seen yet.