I remember years ago a Times reporter published something I knew was false, something they had been told by a trusted (to them) source in Congress.
Their logic was, basically, this person wouldn't lie to me because if they did I would expose them. Since I would expose them, a kind of nuclear retaliation, they wouldn't lie. Therefore they aren't lying. QED.
I have seen precisely one source get burned for lying. That was, amusingly, Ann Coulter getting busted by Howie Kurtz.
I don't know if the reporter really believed this, but in practice what it means is that there are sources they pretend to trust, and ones they treat with skepticism. True for states, true for politicians, true for lobbyists, true for staffers...
I'm too lazy to check, but I would bet a huge tell in international coverage is which sources get embodied into a state ("Israel" or "United Kingdom") and which are labeled as mere people.