To the point:
Any act that intentionally undermines or destroys one of those ends, ...
How is it that NFP does not fit that bill? It certainly does intentionally undermine the chance of producing life.
NFP is periodic abstinence. It is not a sexual act altered in order to undermine procreation. A sexual act thwarting procreation, is a sexually perverse act, as in the sin of Onan. Abstinence is not a sex act at all: far less is it a sexually perverse act.
The difference betwen contraception and abstinence, is like the difference between destructive speech, and silence. A person who says something against you, is engaging in destructive speech. A person who says nothing, is simply exercising self-control in order--- in this analogy --- to avoid the wrong kind of speech.
What I like about NFP is that when you have sex, you engage in it "wholly," and when you abstain, you abstain "wholly." Both the intercourse and the abstinence are respectful of the "wholeness" and "holiness" of the act. Scripture says there is a time to embrace, and a time to refrain from embracing.
And since women are designed to be periodically fertile/infertile, using the periodic ebb and flow with intelligence and grace, is respecting (not overriding) the design.
I think the patterns of women's fertility are providential, something you try to harmonize with, not somthing you try to chemically or mechanically smack down. I thank the Designer of women for the way we are designed.