It is rather. It's apparent from developing Experimental why they did, though: trying to run a bottom-up simulation on anything larger would have got very slow very quickly - the computational effort required increases exponentially with the number of buildings, and linearly with the number of different sorts of things being simulated, and, in Sim City (2013) there are a very large number of agent based bottom up simulation layers. Trying to route traffic, electricity, water, sewage, health, fire coverage, crime, police coverage, air pollution, water pollution, jobs, goods and a whole lot more things through a very large number of buildings would have overwhelmed even the fastest of computers.