DialogHost.WaitFor* methods not waiting for animation to finish #4086

private async void Button_Click(object sender, RoutedEventArgs e)
{
    var dialogContent = new Button()
    {
        Content = "Close",
        Margin = new Thickness(400)            
    };
    dialogContent.Click += (_, _) => DialogHost.Close("RootDialog");

    await DialogHost.Show(dialogContent, "RootDialog");
    var sw = Stopwatch.StartNew();
    await DialogHost.WaitForClosed("RootDialog");
    sw.Stop();
    Debug.WriteLine($"WaitForClosed: {sw.ElapsedMilliseconds}ms");

    // Do some UI work
    if (App.Current.MainWindow.Background == System.Windows.Media.Brushes.Red)
    {
        App.Current.MainWindow.Background = System.Windows.Media.Brushes.Green;
    }
    else
    {
        App.Current.MainWindow.Background = System.Windows.Media.Brushes.Red;
    }
}