Usually I don't need it. But from my experience I always noticed a bug with AI after 6-8 months. If you block an AI for 7 months so he can't move, when you free him, he will not move anymore (even if he can). So the !!AI script is necessary. In my map Alexander, the main hero had to be attacked by an AI hero on month 9. The AI was behind a border gate all this time. When I opened the gate, he did not attack (he had azure dragons and I had one peasant). This occured only if several months were spent in game. So I had to use !!AI to make him move. I think this command is important to know how it works.