The issue is that he wants to make a huge level. 15km away from the origin is already huge, he will already face problems with precision when the character gets near the edges of the level. That’s why he needs level streaming.
Yes and if the other walls are part of the actor’s main location then these problems might be solved, they are extensions of the middle point. For this he has to transform the meshes to local space of the actor so they all become one but with many components.
I may be wrong but this is my idea.