I believe that code and the annotations is straight from SavageAI - I never made alterations to the slave factions CAI. Specifically with the Yellow Turban event, it's kind of an odd situation. Anytime an army is scripted to spawn and besiege a settlement, they will only attack if either A) they have 'siege weapons' and their spawn/siege script specifies for them to attack, or B) they don't have 'siege weapons' and they have to build ladders/towers/rams over several turns; in the latter case, whether they attack, and when, is totally up to the AI. But, to get the slave AI more aggressive, you would really need to take a look at the Workshop on how to do that as it is a bit outside of my expertise.