See the stream at 1h15: "That other side of the map is real, it is there, and those civilizations are growing and developing. You wont interact with them directly, but because it is the same game world, they are building what you will be dealing with later or interacting with. They even may beat you on a wonder, that has happened to Carl earlier".
So... the map expands during the exploration age, giving you a new world to explore, but this essentially means there are continents separated by oceans, but the game is going on there normally.
This does not answer our questions about pangaea maps though.