The switching of jobs by Jack and Ennis, was almost to me, subtle statement of roles these two men assume from then on.
They were for the first time being more of themselves together. Ennis personality drew him to being the herder, than camp tender, "I wouldn't mind being out here", after seeing Jack's dislike for being with the sheep, he didn't mind it, it was what he used to or enjoyed the aloneness of it being out there.
Jack's nature was more of caretaker, he may not have been very good at it, it apparently was good enough for Ennis, he eats the food Jack prepares, he opens up to him, they become closer. The roles now established, they become more drawn to each other.
Ennis took this with him, into his marriage to Alma, He continue to work with stock, he comes home, but it wasn't to Jack, but to Alma. I wonder how this must have cause him some pang of painful memories, until he sees Jack again.
I'm sorry this way off topic.