This patch groups defensive structures together in the build list. Since they tend to be built later than civic (e.g. house), economic (e.g. farmstead), and military (e.g. barracks) structures, they're listed at the end, just before the Wonder. Wallsets are listed after towers, which are more common.
This is how it looks in game:
It does not affect balance and is basically a follow-up to D2580/rP23548.