I think that we could readily agree that the lead comes from the core in AT. Subtle? Yes, in the hands of an advanced dancer, but on the whole? Well the average standard is pretty modest, generally, and I think that focussing on the leader's chest is actually a step UP from what generally happens: the arms are used, particularly to signal rotation, which brings me right back to the beginning of this topic, and the assertion that that's not what they're for in any dance style.
Interestingly, I constantly find more similarities than differences between AT and Ballroom (so I go against the trend), and would say that the lead in both works in exactly the same way, fundamentally. The differences arise from the particular style requirements, and the actions, typical of each dance.