Nope. You missed the point about abstaining. If no sex act occurs, there is no sin, whether the point is to avoid procreation or not.
"On the other hand, sex between a couple in which the woman had a hysterectomy for health reasons is not at all "open to procreation". Sinful?"
Nope. Just because the woman is rendered infertile by factors beyond her control doesn't mean she is committing a sin by having sex. On the other hand, if she has had a tubal ligation with the specific view of preventing pregnanacy, than she HAS sinned.
I think I understand what you're saying here. But it's a misunderstanding. "Openness to procreation" does not have anything to do with the method's "failure rate." This idea that a method's "chanciness" defines its "openness to life" is a false inference that a lot of people draw. That's why I never use the words "openness to procreation." It can be misinterpreted and cause unnecessary confusion.
What we're looking for here is, what is your stance toward sex? Do you think that healthy, natural sex --- pleasurable, emotionally satisfying, periodically fertile/infertile, expressing "I am yours, you are mine" ---is good the way God designed it? Do you think that human fertility is a holy thing, or do you think that fertility is a design flaw, a disease?
If women's bodies have a design flaw, a disease (fertility), you will attack it with drugs, devices, and surgery, just as if it were cancer, or an infestation of parasites. Contraception is based on the pathology paradigm of the female body.
On the other hand, if fertility is a holy thing, and a good part of a good design, then you practice sexual intercourse during your wife's fertile period when you're willing to accept the gift of a child; and you cherishingly refrain during that time when (for whatever reasons of health or hardship) you could not responsibly accept a child.
Either way it's respectful. It always gives homage to fertility as an awesome gift, because human life is an awesome thing: I could even say access to a fertile woman is an awesome thing, a gift: one which is respectfully accepted, or one which is respectfully declined. It says in an embodied way, "You were made right: I don't want to alter you. I will behave accordingly."
For the most part, contraception is an embodied insult to women. I mean that it embodies the message: if you were made right, you'd be available all the time. But you were made wrong, dammit. You need to be fixed.