Correct, Rust is made in unity and also uses listen server model. Here’s an article talking about how they did their networking. Rust's Networking - Garry's Blog
If I were to guess, I say something about unity lets you load world tiles locally and probably allows for some sort of net culling authority.
that’s not built into the default UE networking model as far as I’m aware. What you could do is use a combination of the default networking model and photon which is now available for unreal.
Not sure at what point in the upgrade path to UE5 we switch to double precision floats, but at that point it will be simple to just do regular level streaming.