They didn't come clean, it's clear from the article they were busted.
They strongly resisted multiple challenges to the obvious problems with his accounts by other writers and organisations culminating in him being arrested for fraud.
https://www.npr.org/2017/09/15/551163406/fox-news-has-yet-to...
They got caught - they didn't come clean.
And now they're trying to milk the fact that they were caught to make themselves sound humble.
You're implying that they should never post a story unless they are 100% certain, which means most stories would never get published, defeating the entire point of journalism. Obviously the threshold needs to be high, you don't want to post every single rumor, but just because they have 1 or 2 correction a year does not mean "they'd rather ask for forgiveness than get permission".
This seems a pretty major failing. Of course, they always seem that way after the fact. And TBH a lot of stories run that can't be verified beyond the tiniest shade of a doubt that are substantially accurate.