I think their point was that engineering is the process of finding the most efficient way to accomplish a given goal given the whole of science and technology with which to accomplish it. In this way, a purely mechanical watch attempting such complex calculations is suboptimal. As such, it's existence is a form of art -- it is engineering only in the sense that the restrictions imposed are themselves non-optimal (for instance, the requirement that purely mechanical mechanisms be used). Something at the pinnacle of engineering would seek to optimise not only the solution, but also the requirements.