highlightFollowsCurrentItem: false (ListView and GreedView) seems buggy

import QtQuick 2.7
import QtQuick.Controls 2.0
Item {
    id: root
    width: 200
    height: 700

    ListView {
        id: list
        clip: true
        spacing: 10
        model: 100
        width: 100
        height: 500
        highlightFollowsCurrentItem : false
        //highlightRangeMode:
        delegate: Rectangle {
            width: 100
            height: 100
            color: "green"
            opacity: ListView.isCurrentItem ? 1 : 0.5
            Text {
                anchors.centerIn: parent
                text: index
                font.pixelSize: 20
            }
        }
    }

    Button {
        anchors.top: list.bottom
        width: 100
        height: 100
        text: list.currentIndex
        onClicked: list.currentIndex = ++list.currentIndex % list.count
    }
}