Different result for implicitWidth and implicitHeight use

import QtQuick 1.1
Item {
    width: 950
    height: 500

    Rectangle {
        color: "green"
        width: loader.implicitWidth+50
        height: loader.implicitHeight+50
        onWidthChanged: print("loader.implicitWidth: " + loader.implicitWidth)
        onHeightChanged: print("loader.implicitHeight: " + loader.implicitHeight)

        Item {
            anchors.fill: parent
            anchors.margins: 15

            Loader {
                id: loader
                sourceComponent: redRect
                anchors.fill: parent
                Rectangle { color: "yellow"; opacity: 0.5; anchors.fill: parent; z: 100 }
            }
        }
    }


    Component {
        id: redRect
        Item {
            anchors.centerIn: parent

            implicitWidth: 200
            implicitHeight: 200
            Rectangle {
                color: "red"
                anchors.fill: parent
            }
        }
    }
}