Qt3D RHI rendere doesn't support ClearBuffers correctly

import Qt3D.Core 2.0
import Qt3D.Render 2.0
RenderSettings {
    id: quadViewportFrameGraph
    property alias topLeftCamera: cameraSelectorTopLeftViewport.camera;
    property alias topRightCamera: cameraSelectorTopRightViewport.camera;
    property alias bottomLeftCamera: cameraSelectorBottomLeftViewport.camera;
    property alias bottomRightCamera: cameraSelectorBottomRightViewport.camera;
    property alias window: surfaceSelector.surface
    activeFrameGraph: RenderSurfaceSelector {
        id: surfaceSelector
        //! [0]
        Viewport {
            id: mainViewport
            normalizedRect: Qt.rect(0, 0, 1, 1)
            ClearBuffers {
                buffers: ClearBuffers.ColorDepthBuffer
                clearColor: Qt.rgba(0.6, 0.6, 0.6, 1.0)
                NoDraw {}
            }
            Viewport {
                id: topLeftViewport
                normalizedRect: Qt.rect(0, 0, 0.5, 0.5)
                CameraSelector { id: cameraSelectorTopLeftViewport }
            }
            Viewport {
                id: topRightViewport
                normalizedRect: Qt.rect(0.5, 0, 0.5, 0.5)
                CameraSelector { id: cameraSelectorTopRightViewport }
            }
            Viewport {
                id: bottomLeftViewport
                normalizedRect: Qt.rect(0, 0.5, 0.5, 0.5)
                CameraSelector { id: cameraSelectorBottomLeftViewport }
            }
            Viewport {
                id: bottomRightViewport
                normalizedRect: Qt.rect(0.25, 0.25, 0.75, 0.75)
                ClearBuffers {
                    buffers: ClearBuffers.ColorDepthBuffer
                    clearColor: Qt.rgba(1, 0., 0., 1.0)
                    CameraSelector { id: cameraSelectorBottomRightViewport }
                }
            }
        }
        //! [0]
    }
}