Decision trees are one of the oldest forms of AI! There are even algorithms to automatically form decision trees, though you don't need ML to have AI.
Those algorithms were only called machine learning and it's the opposite. Before the marketers got ahold of it we reserved AI for the actually intelligent, sentient, full strength vision of intelligent systems. We now talk about general AIs and A[Super]Is.
Indeed; As I recall, I mentioned GOFAI in the interview and got amused agreement.