I must admit as to being unsure precisely what you are referring to in terms of the different plot diagrams that you mention. However, I wonder if the "chain" that you refer to could indicate a chain linking different events to each other. What is clearly evident from this story is the way that cause and effect operates to create the continual rebuilding of the city walls as each city vies with each other for dominance. Note how the beginning of the story feels compelled to rebuild his city walls so that the "pig" that the other city's walls resemble will not "devour" the orange that the Mandarin's city's walls resemble:

Demons lurked everywhere, Death swam in the wetness of an eye, the turn of a gull's wing meant rain, a fan held so, the tilt of a roof, and, yes, even a city wall was of immense importance. Travellers and tourists, caravans, musicians, artists, coming upon these two towns, equally judging the portents, would say, "The city shaped like an orange? No! I will enter the city shaped like a pig and prosper, eating all, growing fat with good luck and prosperity!"

Thus the chain analogy seems to be most fitting. Each change of the city walls provokes a change in the city walls of the other city, until only the common sense of the Mandarin's daughter saves both of the cities from destruction.