But it could disrupt their ability to communicate for a critical period of time. They have their people scattered all over, most of them not very bright bulbs to begin with, afraid that their messages will be easily translated. That might even be better than having the codes and not letting them know about it.
Short term. But long term, you sit on it and don't announce it to the world. You use those code words to break other code words, and harvest the information to the point you're translating their messages. That would outweigh any "possible" disruption of communications.