Currently, StreamingMesh models are not occluded when they are entirely hidden behind something.
This means that using StreamingMesh models at all has an unnecessarily steep detrimental impact on game performance, since they are visible even while occluded, while their fully rendered counterparts would not be.
If I turn off streamingmesh on these models, they are either not visible since they’re streamed out, or they are occluded.
Expected behavior
I would expect the entire StreamingMesh to be treated as a single entity that can be occluded, like any basepart. Even if with lower precision, even AABB would be good enough.