As far as i can see with the debug mode enabled in the config, slabs and stairs are not considered occluding shapes, which results in a lot more entites being rendered in smaller builds

This is not planned for now, maybe in the future with a rewrite that uses spacial partitioning. With the current implementation, this is not possible (cache would need to be 8 times as big, and every ray multiple times as long, that would nuke performance, more than the gain from culling).