Still call it “contraception” if you will (afterall scientists still call aircraft blackboxes “blackboxes” when in fact they are bright orange). Its just a label.
This may be one of our fundamental points of separation - the semantic of “contraception”.
As it pertains to the actual word itself (contraception), most would argue that NFP comfortably fits as an exemplar and isn’t even remotely a stretched euphemism.
As you mentioned, Catholics do seem to have a more nuanced definition of this word than is found in, say, Oxford’s dictionary.
As I see neither side really budging, this will likely be a sticking point until either language drifts the word into obsolescence or Catholics pick another descriptor.
I believe it is relatively easy to describe/identify the specific/qualitiative difference between NFP and Onan.
I would agree.
As you seem to speak at some length about Onan, I would like to state that I’m not particularly married to onanism as a “solution”. I readily agree that it frustrates the procreative aspect of sex in a way that lacks artifice, but then also creates room to debate whether or not the marital act was thus completed due to procreative frustration and whether that is even an important standard.
I do find it interesting, though, that our Protestant friends don’t think Onan was struck down because he placed his seed in the dirt. They argue he was killed for deceiving his wife/sister-in-law and failing to uphold is familial oath and duty. The spilling of seed was merely coincidental.
This makes me think I have not quite understood your argument as it seems a non sequitor?
The line about failure was included to further proof the intent of the NFP couple to frustrate the procreative aspect of relations. As you wrote “Yes NFP even amongst the experienced is only 97-99% successful.” then that means 1-3% are not and this is, statistically, a failure rate. Nothing more intended.
Mr NFP does not “contra” the sex act itself, though as you say he certainly “contra’s” the normative biological results by craftily taking advantage of the “blanks” of nature. Crafty though it may be the Church sees nothing immoral in this.
Then in fairness, the Church doesn’t seem to require that the marital act be open to life. It can be as closed to life as humanly possible with full, unveiled intent - so long as no artifice is used and climax occurs fully and properly coupled.
Which is fine, I suppose. But that’s not the line we typically hear “out in the world”.