Speaking as someone who is a child of a toxically acrimonious divorce and custody arrangement, I can say with certainty that any distortion of reality impedes a child's ability to foster resilience in the face of a harsh reality. It hinders their emotional development as well, and could possibly lead to a lifetime of resentment. No child deserves that kind of furture.

In this case, the cat was out of the bag so there was no point in keeping silent. The kids deserved the truth, so as to be able to properly process the reality that their family life was ripped away from them so abruptly. What's more both parents deserve blame for trying to coerce promises of silence on the issue.