New items dropped on a tab control don't go in selected tab item Declined - Not Valid

When I drop a new control from the Tool Box on an SF tab control, it is placed below all the existing tab items rather than within a selected tab item. For example, in this case, I had the second tab item, "Output Pins," selected and dropped a SdDataGrid on it. Instead of going to the selected tab item, as I expected, the control was placed below all other items. Here is the result:

        <syncfusion:TabControlExt
            Grid.Row="1"
            HorizontalAlignment="Stretch"
            VerticalAlignment="Stretch"
            CloseButtonType="Hide"
            ShowTabItemContextMenu="False">
            <syncfusion:TabItemExt CanClose="False" Header="Input Pins" />
            <syncfusion:TabItemExt CanClose="False" Header="Output Pins" />
            <syncfusion:TabItemExt CanClose="False" Header="Parts" />
            <syncfusion:TabItemExt CanClose="False" Header="Header Text" />
            <syncfusion:TabItemExt CanClose="False" Header="API Text" />
            <syncfusion:TabItemExt CanClose="False" Header="Description Text" />
            <syncfusion:TabItemExt CanClose="False" Header="File View" />
            <syncfusion:SfDataGrid/>
        </syncfusion:TabControlExt>

The grid appears within the GUI view as a new tab item without a header. Here's a screenshot:

This isn't a real problem because I usually type in controls down in the XAML view, but I noticed this while looking at the SF controls. It might be something someone wishes to address.