I don't agree with this at all. These characters were in a sexual love affair, I don't see it as having a dirty mind to perceive that their dialogue alluded to sex also. I mean, to tell your post-coital lover that you "wrung it out about a 100 times" thinking about him: if that's not about masturbation, then I must have the mind of a gutter rat! Peace.
Well, as a person who lives on the other side of the world, Aussie Chris, you can disagree or agree with anything about the meaning of originally American coined words and expressions in the Western US States.
I just think that Ennis Del Mar just thought all the sex he had with Jack up on Brokeback Mountain, which he enjoyed, and his wringing it out a hundred times might have been his remembrance of each of those times and he tried at least a hundred times to attempt to figure out, aka wring out, why he liked doin' it with Jack.
I have met people in real life who claimed to be straight; but, they said they just didn't understand why they liked to have, and wanted to have, sex with certain guys.