Hi Tony, I stumbled onto this conversation when I tried to look you up. Had not noticed your comments recently and hope that you are well.
After enjoying the comments by all, I settled in on the Why question, which I think is always the best one. It would not surprise me if AA wanted to convey the repetition of arches in the scene. I see the arch at the end of the road, the arch of Half Dome over the tree tops arched under the snow, and I see arches over the row between the rows of trees. All the archways take me more or less toward Half Dome. The proximity of HD to the top edge makes sure we notice it.
The branch sticking up into the sky? Well the sky had not much else going on so why not showmoff the branch?
I wonder if we can get @William_Neill to join the discussion? Bruce Birnbaum is not shy about crowding the top edge, either.