There's something incredibly Boston about this to me: downtown is so good at doing that layered, oblique thing where every era of the city's history is visible at once. These pictures reinforce that from nearly every angle, the observer's eye is tricked into thinking these are two different buildings, with the base building occluding the addition. Even up close it somehow appears that the new building is behind the old one. I think it adds depth to the fabric.
This is a counterfactual because we don't know what it would have looked like for this addition to respond to its host with imitation, but I think it makes a convincing case that having no architectural response at all can be a successful strategy. I don't think it could work everywhere but in our windy downtown it does.