There is something to be said though to OP's point where it's actually better to do nothing than an AI.txt because it can give a false sense of security, which is obviously not what you want.
Anytime a business is caught using that content, they can't claim that they used publicly available information, because the ai.txt specifically signalled to everyone in a clear and unambiguous manner that the copyright granted by viewing the page is witheld from ai training.