FileDialog from Qt.labs.platform module cannot update selectedNameFilter.index correctly

A simple reproducer:

ApplicationWindow {
    visible: true
    width: 400
    height: 200

    Button {
        text: "Open"
        onClicked: dialog.open()
    }

    Platform.FileDialog {
        id: dialog
        title: "title"
        fileMode: Platform.FileDialog.SaveFile
        nameFilters: ["csv file" + " (*.csv)",
        "text file" + " (*.txt)"]
        onAccepted: {
            var n = selectedNameFilter.name
            var i = selectedNameFilter.index
            console.log(`Name: ${n}, Index: ${i}`)
        }
        // selectedNameFilter.onNameChanged: {
        // }
        // selectedNameFilter.onIndexChanged: {
        // }
    }
}

Run the sample, click button to open FileDialog for the first time, then save file. Even if one selects "save type as" from drop-down, the output to console is "qml: Name: , Index: -1" for the first run. The output is correct from the second run though.

Current workaround:
1. Explicitly bind selectedNameFilter.index, as what is done in:
https://doc.qt.io/qt-6/qml-qtquick-dialogs-filedialog.html#selectedNameFilter-prop
2. Use FileDialog from QtQuick.Dialog module. The non-lab version behaves correctly.
3. Uncomment signal handlers, i.e. trying to read selectedNameFilter properties.

Reason:

QQuickLabsPlatformFileNameFilter *QQuickLabsPlatformFileDialog::selectedNameFilter()

The function to create the selectednameFilter won't be called unless QML tries to READ m_selectedNameFilter. So for the first run, m_selectedNameFilter does not exist yet. Only after the 1st run there is a valid m_selectedNameFilter.

Personally speaking, the behavior of non-lab version is preferable.