Sometimes, it's just easier to play into a narcissist's lies. I'll admit it. I'm guilty of it on more than one occasion. If I was dealing with a "normal" co-parent (and by that I mean someone who had all the marbles in the right place), we could have a free exchange of information about the children, their lives, and the custody exchange.
But I'm not dealing with a "normal" co-parent. So, sometimes, I have to play the game. Or maybe "have to" isn't the right words. Sometimes, it's just easier to play the game. In some cases it works in my favour.