The birth of AI was still a mystery for level 3 space civilizations because this involved the Chaos Theory. Even though the Chaos Theory was already present in the human knowledge before humanity left Earth, it didn't mean that they had understood and mastered it. This was similar to the theory of the Big Bang. Humanity had speculations about that since the middle-ages, but did it mean they understood that then?
Every civilization had one important feature: a clear, logical understanding of the world. You couldn't say one plus one equals two one second and then one plus one equals three the next, this wasn't scientific.
