The house models themselves might use the same geometry and textures, but if you pre-bake any lighting then that’s a unique texture across every single surface in the world that can’t be deduplicated.

Depending on how the models are expressed in the environment, theres a good chance they end up as triangle meshes with unique coordinates by the time the running game eversees them.

Unless it’s changed a lot since I worked in game dev, models absolutely are instanced but poly counts, texture resolutions and number of textures have gone through the roof. You used to have a texture and maybe a light map, now you have separate diffuse, specular, bump, glow, decals, etc. etc.

Everyone’s doing physically based rendering, so now it’s base color, roughness, metallic, and specular. Plus the glow, decals, etc.

Wouldn’t they want to keep reused objects instanced for performance, or is there some other advantage to just meshing everything out into a unique set of level parts?