That's in the short story and the movie.
I don't think that really says much, lots of couples do anal at different times, with different types of satisfaction with it. Just depends on the people, speaking as one half of such couple.
HE also tells Jack outloud in the short story that he likes doing it with women too--it just isn't like doing it with Jack.
So I don't think you are changing my mind any more than I am changing yours.
But I know what the book says too, and it never said he doesn't love Alma, that is simply someone trying to put thought patterns into the character on their own.
And considering a lot of what Annie wrote gives us leaway to do just that-to each their own.