Data Point Selection Modifier on XyDataSeries

Hello, I am trying to use the default DataPointSelectionModifier on a line chart with a DataSeries of type XyDataSeries<‘DateTime, double’> as in the example suite HERE . It seems to work fine out of the box if the DataSeries is of type XyDataSeries<‘double, double’>. Am I missing something as to why this modifier is not working with the former data type?

Relevent code is:

CustomChart.xaml:

<sci:SciChartSurface x:Name="customChart"
                         Grid.Column="0">
        <sci:SciChartSurface.RenderableSeries>

            <sci:FastLineRenderableSeries Name="lineRenderableSeries"
                                          Stroke="#4AB748"
                                          StrokeThickness="1">
                <sci:FastLineRenderableSeries.PointMarker>
                    <sci:EllipsePointMarker Fill="#138A43" />
                </sci:FastLineRenderableSeries.PointMarker>
                <sci:FastLineRenderableSeries.SelectedPointMarker>
                    <sci:EllipsePointMarker Fill="#C4ECA0"
                                            Width="12"
                                            Height="12" />
                </sci:FastLineRenderableSeries.SelectedPointMarker>
            </sci:FastLineRenderableSeries>
        </sci:SciChartSurface.RenderableSeries>

        <!--  Create an X Axis with GrowBy  -->
        <sci:SciChartSurface.XAxes>
            <sci:CategoryDateTimeAxis DrawMajorBands="True"
                                      GrowBy="0.1, 0.1"
                                      AxisAlignment="Bottom" />
        </sci:SciChartSurface.XAxes>

        <!--  Create a Y Axis with GrowBy.-->
        <sci:SciChartSurface.YAxis>
            <sci:NumericAxis DrawMajorBands="False"
                             GrowBy="0.5, 0.5"
                             CursorTextFormatting="$0.00"
                             TextFormatting="$0.00" />
        </sci:SciChartSurface.YAxis>

        <!-- Setting IsEnabled enables or disables a modifier in the Toolbar -->
        <sci:SciChartSurface.ChartModifier>
            <sci:ModifierGroup>

                <sci:DataPointSelectionModifier Name="PointMarkersSelectionModifier"
                                                IsEnabled="True"
                                                SelectionFill="#B1B5B2B2"
                                                SelectionStroke="#009E9C9C" />
            </sci:ModifierGroup>
        </sci:SciChartSurface.ChartModifier>


    </sci:SciChartSurface>

CustomChart.xaml.cs:

private void OnDataSeriesChanged(DependencyPropertyChangedEventArgs e)
    {
      var inputDataSeries = e.NewValue as XyDataSeries<DateTime, double>;

        var dataSeries = new XyDataSeries<DateTime, double>();

        dataSeries.Append(inputDataSeries.XValues, inputDataSeries.YValues, dataSeries.YValues.Select((x) => new MyMetadata { IsSelected = false }));

        lineRenderableSeries.DataSeries = dataSeries;

    }

MyMetaData.cs:

public class MyMetadata : IPointMetadata
{
    public event PropertyChangedEventHandler PropertyChanged;
    public bool IsSelected { get; set; }
}

With this implementation I am able to individually select datapoints and select multiple datapoints with ctrl/shift but am unable to drag select multiple datapoints.

If, as in the example suite, I change the default XAxis to:

<sci:SciChartSurface.XAxis>
            <sci:NumericAxis 
                             DrawMajorBands="True"
                             GrowBy="0.1, 0.1"
                             CursorTextFormatting="0" />
        </sci:SciChartSurface.XAxis>-->

and of course change all the relevant datatypes in CustomChart.xaml.cs from XyDataSeries<‘DateTime, double’> to XyDataSeries<‘double, double’> everything behaves as expected.

Am I missing something to make the DragSelection work out of the box with the former data type without having to make a custom modifier?

Thank you in advance for your help.