"A fact that's missing critical context can travel half way around the world while the full context is putting on its shoes."
The same fundamental concept is at play here.
Supposedly Comey violated it because some FBI agents were already illegally leaking it to Guliani and he was sure Clinton would win anyway
https://www.politico.com/magazine/story/2019/08/02/joe-biden...
https://www.politico.com/news/2020/03/09/james-biden-health-...
https://www.newyorker.com/magazine/2019/07/08/will-hunter-bi...
https://www.nytimes.com/2019/05/01/us/politics/biden-son-ukr...
If the story is true. If it's a fabrication - as they allege, and given that Fox News passed on it (https://www.independent.co.uk/news/world/americas/us-electio...) and the Post's reporter didn't want his byline on it (https://www.nytimes.com/2020/10/18/business/media/new-york-p...), seems reasonably likely - they didn't hear about it until last week.
We learned this doesn't work all that well with the Comey letter eleven days before the 2016 election. "We've reopened the Hillary investigation" turned into "oops, nothing new" a few days after the election.
"A lie can travel half way around the world while the truth is putting on its shoes."