MouseEvent param or positionChange signal of MouseArea always has Qt.NoButton value

import QtQuick
MouseArea {
    width: 600
    height: 600
    onPositionChanged: (event) => {
        console.log(event.button)
    }
} 

If I press left mouse button and drag mouse cursor over window, following is printed in console:

qml: 0
qml: 0
qml: 0
...

According to https://doc.qt.io/qt-6/qml-qtquick-mousearea.html#positionChanged-signal it should contain buttons pressed while dragging: