I think it's the character trait that makes the AI pay closer attention to character descriptions that lets this happen. I have been having fun with it.
I think when it comes to things like "all foxes are blue," you need to use specific character names since the AI sometimes struggles with who is a fox and who isn't. I have had dialog where a character calls themselves a wolf or me a fox. So if you are targeting specific characters it might be best to name them in the description. Which is why I wish I had more than 400 characters to work with.
I 100% like this little discovery as it lets us add a little flavor to the world in ways that is not just our own character.