probably a staged fake leak as part of their sabre rattling
Hmm, not necessarily. The US wanted to use nuclear weapons in Korea, they wanted to sell some to the French in Vietnam and then wanted to use them during the Tet offensive, they wanted to sell them to the British, they wanted to use them during the Cuban missile crisis. I can find it probable that they would also consider using them in China, especially around that time.
Parenti talks about it here: https://www.youtube.com/watch?v=xSLQBM2fCvY, at around the 53 minute mark. Also that allows me to plug my video :)
Unfortunately, he doesn’t explain why they did not use the weapons (whether the French, British, or Amerikans). However, the US has never (and refuses to) signed a no-first-pledge agreement because they use(d) their nuclear capabilities as a threat.