positionViewAtIndex() from Component.onCompleted doesn't Center

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    ListView {
        id: lv

        anchors.fill: parent

        model: 1000
        clip: true
        delegate: Text {
            width: lv.width
            text: index
        }
        // Doesn't center - the 500th delegate as at the viewport edge
        Component.onCompleted: positionViewAtIndex(500, ListView.Center)
    }
}