He's saying that the AI automatically picks an heir for him. And the AI generally picks a bad heir. So he is forced to make the man who the AI picked as heir lose influence to choose the man he really wanted as heir. His problem, as I understand it, is not anything to do with the existence of the "disinheireted" trait, only that in order to choose the heir that he would like, the man that the AI picked gains the trait. He is powerless to pick the heir that he wants without the AI selected heir becoming disinheireted.