I'm not sure what the thinking is exactly, but having just watched the game again I can only say: Ryder nearly won us the game in the last quarter - I think he was the key player on the ground in the 4th. So the only reason he was spared as much time in the ruck before that would be because, A: They are trying to get Ryder more experience as a key forward/thought Carlisle would actually do something useful. B: They were trying to get Bellchambers to wear Jolly down so Ryder could come over the top of him in the last. C: They don't trust Bellchambers up forward/didn't think Bellchambers would get beaten as badly as he did. Given that, Hille is a better match for the team, no matter what the reason was.