They just added "on this issue" to it. Doesn't seem to be a big deal - they are just making bit more explicit what was already implied. It would be different if they had removed the line completely or changed their stance 180 degree.
Which in itself could mean they were initially eager to release it (instead of letting it rot on a shelf or something), and/or that it was written with a hot pen, if you know what I mean. "Lost all credibility" [on everything ever] is something I might say, but it's not something I would expect to read in a decent newspaper. Someone got a bit emotional over this and I salute them for that; that they later decided to be a bit more smart and effective about it doesn't take anything away, it just adds to it.
edit/addendum: Just consider what it would literally mean, he lost crediblity on everything; a feast for any and all republicans, for starters. I mean, does this mean gay marriage was a mistake, too? Some would happily use this as water on their mills with unrelated issues.
There's no reason that this diminishes their credibility on, say, health care reform. It's a totally different set of people, and a fundamentally different agenda.
If this is a stupid thought process I apologize, I am slightly sleep deprived.
Interesting view. I didn't get that implication at all. When I read it I was quite amazed, and impressed, that the Times had flat out said that. Damn straight, I thought.
As earlier commenters have noted the original story was pushed out quickly, and later refined. This is totally normal in all newsrooms, and if you diff boring, non-controversial stories, you'll see the same thing--though perhaps to a lesser degree due to the fact that there's less of a rush to get out, say, a travel piece, compared to one with national import.
Full disclosure: I worked at the NYTimes for two years as a developer in the newsroom. NYT editors and reporters are, almost universally, smart, careful, well-intentioned people.