I think that was it. In the end you're really caring about what will have the biggest impact on the audience, and having Rohan's theme then wouldn't work as well as Reclamation. It's just like having Leia's theme during Ben's death. It doesn't make sense, but it sounds brilliant. EDIT: Dang it, you beat me to that last point, Luke! Actually, I forget where I read it exactly, but the reason John Williams put Leia's theme at the point of Obi-Wan's death is because her message was responsible for him having to face his former apprentice by leaving Tatooine. Pretty cool if you ask me. Also, if you listen carefully at the point where Leia inserts the plans into Artoo, you can hear a slight rendition of the Force Theme, since it is to Obi-Wan she is sending the plans.