DialogButtonBox not regenerating layout on change of child Button width

import QtQuick 2.7
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.3
import QtQuick.Window 2.2
import QtQuick.Controls.Material 2.2

Dialog {
    id: root

    title: "DialogButtonBox not regenerating child button layout on change of child width"

    height: parent.height*2/5

    width:  parent.width*2/3

    modal: true

    standardButtons: Dialog.Cancel;

    footer: DialogButtonBox {

        delegate: Button{}

        Button {
            text: "Button A"
        }

        Button {
            id: buttonB
            text: "Button B"

            Timer {
                interval: 5000
                repeat: false
                running: true
                onTriggered: {
                    buttonB.implicitWidth = 150
                }
            }
        }
    }
}