I do think Ennis didn't tell Alma anything of emotional importance to him about his summer job on the mountain; - but I do think he had to tell her something.
Well, he might have just said "hunnh" or "mmm-hmmm." I mean, this is Ennis, after all.
I would assume that, if Alma knew him well enough to be engaged to him, she wouldn't have expected any kind of long, detailed story from him.
Somebody up-thread mentioned that the rodeoing might have just slipped out... that Ennis pauses, as if to collect himself just a little bit, before he tells the "fishing buddy" lie. As if Ennis let out more about that private part of himself than he ever intended to, in the heat of the moment when he saw Jack's postcard.
However, regarding the first one, I'm wondering -- does Ennis say Brokeback" when he's talking to the Twists about the ashes (I can't remember exactly! But isn't it something like, "I come by to offer to scatter Jack's ashes on Brokeback Mountain, like his wife said Jack wanted"?)
Doesn't Ennis say "Brokeback" when he's talking to Lureen? After she says that Jack wanted his ashes scattered there, Ennis manages to choke out something like "Me and Jack herded sheep up on Brokeback in '63." (Don't have the screenplay book in front of me, and can't remember a thing without a written reference.) But I think the point you made works in either case -- Ennis is sort of quietly acknowledging to Lureen that there was something important between him and Jack, even though neither one says anything directly about it.
(That was the line that did me in the first time I saw the movie, by the way. The look on Ennis's face when he finally says "Brokeback" there in that little lonely public phone booth....
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