If a country creates nuclear weapons and no one officially acknowledges them, do the weapons exist?

This piece, presuming it is not based on fluff, is interesting. However a sentence from this section baffles me, in italics:

Now North Korea’s supreme leader, Kim Jong Il, has the potential to kill millions in Japan as well as the South, and to lay waste US bases and airfields in both countries. It will force military strategists to rethink plans for war in Korea and significantly increase the potential costs of any intervention in a future Korean war. The shift from acknowledging North Korea’s nuclear weapons development programme to recognising it as a fully fledged nuclear power is highly controversial. South Korea, in particular, resists the reclassification because it could give the North greater leverage in negotiations.

Is that really all you need to do to neutralize nuclear threats? Just pretend they aren’t there? Or is the author suggesting that South Korean leaders are suffering from cognitive dissonance and have great psychological resistance to facts that would weaken their negotiating positions?