It's just that I don't agree with his conclusion that "civil engineering, in practice, has not made the leap to layered cities", which implies that layered cities are desirable. The metabolists had them, Archigram experimented with them (The Plugin City), most imporantly Yona Friedman. They were not implemented because of cost (see Dubai) or because they were to complicated (see Beijing), they were not implemented because they would require either a common agreement on planning and design, or alternatively a single building pattern. Both are almost impossible to reach in a free world, where the market decides and risk control is a central element of planning. Betch Andres-Beck (another Theater student, quoted by Kent Beck) points out "It's extremely difficual to reverse progress in the construction world [...] asymetry of costs shapes the activities". In a cost-driven world, risk is key. In civil engineering this means decisions are literally fixed as the risk is on CAPEX - in software enginneering this means adaptability as the risk is on OPEX.
Geoff says it better than I could in his take on Archigram:
Architecture can reshape how we inhabit continents, the planet, and the solar system at large. Whether or not you even want inflatable attics, flying carpets, and underwater eel farms, the overwhelming impulse here is that if you don't like the world you've been dropped into, then you should build the one you want.