atz, I'm quoting this from Annie Proulx:
"Later there were some disagreements. In the written story the motel scene after a four-year hiatus stood as central. During their few hours in the Motel Siesta, Jacks's and Ennis's paths were irrevocably laid out. In the film that Ang Lee already had shaped in his mind, the emotional surge contained in that scene would be better shifted to a later point and melded with the men's painful last meeting. I didn't understand this until I saw the film in September 05 and recognized the power of this timing."
Hope that answers one of your questions.