Is this a bug or I'm doing it wrong? (resizing an item when resizing a window)

Edit: I've missed to mention that I am using Qt 5.2

Here is the qml file from the OpenGL under Qml example:

Code:

//! [1]
import QtQuick 2.0
import OpenGLUnderQML 1.0
 
Item {
    id: rectangle1
    width: 320
    height: 480
 
    Squircle {
        SequentialAnimation on t {
            NumberAnimation { to: 1; duration: 2500; easing.type: Easing.InQuad }
            NumberAnimation { to: 0; duration: 2500; easing.type: Easing.OutQuad }
            loops: Animation.Infinite
            running: true
        }
    }
//! [1]
//! [2]
    Rectangle {
        y: 0
        height: 80
        color: Qt.rgba(1, 1, 1, 0.7)
        radius: 10
        anchors.left: parent.left
        anchors.leftMargin: 10
        anchors.right: parent.right
        anchors.rightMargin: 10
        anchors.bottom: parent.bottom
        anchors.bottomMargin: 10
        border.width: 1
    }
}
//! [2]

And here is the same with a default hello world project:

Code:

import QtQuick 2.0
 
Item {
    id: rectangle2
    width: 360
    height: 360
    Text {
        text: qsTr("Hello World")
        anchors.centerIn: parent
    }
    MouseArea {
        id: mouseArea1
        anchors.fill: parent
        onClicked: {
            Qt.quit();
        }
    }
 
    Rectangle {
        id: rectangle1
        y: 235
        height: 97
        color: "#da8686"
        anchors.bottom: parent.bottom
        anchors.bottomMargin: 10
        anchors.right: parent.right
        anchors.rightMargin: 10
        anchors.left: parent.left
        anchors.leftMargin: 10
    }
}

And I'm attaching a screenshot too. The former doesn't work and I don't see any problem in the code. BTW. I am using the MinGW distribution.

I think there is a problem with anchors with this particular example (OpenGL under QML) and maybe that's a related issue.
The idea is to make a rectangle that re-sizes with the window.

If its not my oversight then I guess I should report a bug. I'm waiting for your opinions.

Please see the screenshot about the actual result: