That's what I mean. His "if" here implies that the situation he discusses exists and can be accurately determined, under emergency conditions, by persons with limited knowledge of fertility signs and other relevant facts.
I don't believe this is possible. I've been charting for Natural Family Planning for over ten years, and I have two children whose date of conception I simply could not determine, based on my recorded observations. And my experience isn't unusual among the women I know. Identifying ovulation and fertility, and placing a date of conception appropriately in the cycle, can be quite complicated.
Either the Archbishop isn't aware of these facts, or he's endorsing a "Let's just assume ... our intentions are honorable ..." approach regarding a possible conception. If that's the case, I think he should admit that up front.