Size set in Window{} is not respected in desktop mode

bq M10 rc-proposed r111

If I set width and height in Window component and run the app on tablet in desktop mode, the window size is not as I set.
I set width and height to be units.gu 70x70 but the result is 60x47. See the screenshot please. When I try the same app on my desktop running 16.04 the result is correct (70x70).

Code I used:

import QtQuick 2.4
import Ubuntu.Components 1.3
import QtQuick.Window 2.2

Window {
    id: root_window

    visible: true
    title: i18n.tr("My cool app's name")

    width: units.gu(70)
    height: units.gu(70)

    minimumWidth: units.gu(40)
    minimumHeight: units.gu(40)

    MainView {

        // Note! applicationName needs to match the "name" field of the click manifest
        applicationName: "windowsize.mivoligo"
        anchors.fill: parent

        Text {
            id: window_size

            text: "width = " + root_window.width / units.gu(1) + " height = " + root_window.height / units.gu(1)
            anchors.centerIn: parent
        }
    }
}