[REG 5.15.2-6.2.3] Wrong rendering of semi-transparent text if Text.NativeRendering is used

import QtQuick
import QtQuick.Window

Window {
    width: 640
    height: 480
    visible: true
    color: 'transparent' // important! see comment below for details 

    Rectangle {
        anchors.fill: parent
        color: 'blue'

        Text {
            anchors.centerIn: parent
            text: 'TEXT'
            font.pixelSize: 218

            opacity: 0.4
            renderType: Text.NativeRendering
        }
    }
}