I think Kishimoto didn't think that far ahead during that time, so he's retconning minor stuff like this, take for example the sealed door at the Naka Shrine, it was never shown to have existed during Sasuke's flashback (it was just a carpet on the floor) but it just so happens to have been there when Sasuke and Oro arrived there. Not to mention that he retconned Sasuke to have awaken the Sharingan during the Uchiha Massacre Incident, it's because he wanted Sasuke to have accessed the Tablet only by possessing the Sharingan (thus locking Oro's capability to reverse the Shiki Fuujin by depriving him access to the Tablet) Kishimoto is straightening loose ends to the plot I thinkThe parts that interested me the most were about the RDS reversal and the tablet. Perhaps the tablet was required for the process to be successful. I also loved the fact that you found that bit about Oro saying there was one other way to revive his arms. However, I don't think it was this method he was talking about. That was way back in part one and Oro had very little time at that point to have come up with the idea. Its more logical that he came up with it between part 1 and 2 considering he had a lot more time to research it.
In addition, I don't think Kishi had even come up with that plotline at that point. This idea seems to have come to Kishi more recently rather than way back in part one. So I think Oro was referring to his body transfer technique at the time, not the RDS reversal.