I think hes talking about the conditions for a building be able to be built. For example for walls you need the previous teir. In RTW all buildings either had requirements or no requirements. Wheras in the EB build hes talking about some of the needs for a building being able to be built is not having a building. Like if you dont want sparta to have walls you could have a unique building that makes it impossible for sparta to make walls by having in the walls properties that in order to build it the city must not have the unique building that sparta has.

They might use different methods though.