Mouse events not propagated to Wayland clients

Run attached QML files:

qml compositor.qml &

and

QT_WAYLAND_DISABLE_WINDOWDECORATION=1 qml client.qml -platform wayland

Expected output would be that clicking on the blue rectangle would print "Client: Clicked", since propagateComposedEvents is set to true on the compositor's topmost MouseArea. This works at least for the orange rectangle within the compositor. However, the ShellSurfaceItem doesn't propagate the event to the client. Debugging Wayland shows that wl_pointer.motion events are sent to the client, but no wl_pointer.button events.