My God, that was just an example. The objects are indeed rendered differently (probably a bug in the inerpreter). The pedestrian zone area nonsensically overlays buildings and other areas. That's why the cutout in its area. It's pointless to divide the area into several smaller areas and draw the embedded objects, when it is possible to make the embedding in the area to make them visible.
Is there actually a green area (e.g. grass) in the area? Yes there is, therefore it must be visible or not?