Difference between Thread in WinForm and WPF

Question

I have a Task that update UI in a window. But I don't understand behavior of Thread in WinForm and WPF.

In MainWindow I have two buttons, one that starts Task and one that opens a new window.

private void btnOpenWindow_Click(object sender, RoutedEventArgs e)
{
     var window = new Window();
     OpenedWindow = window;
     window.ShowDialog();
}

private void btnRunTask_Click(object sender, RoutedEventArgs e)
{
     Task.Run(() =>
     {
        //If I call UpdateOpenedWindow() with Dispatcher, CheckAccess() is true
        //this.Dispatcher.Invoke(() => UpdateOpendedWindow());
        UpdateOpenedWindow();
     });
}

private void UpdateOpenedWindow()
{
     if (!OpenedWindow.Dispatcher.CheckAccess())
     {
         //Update UI like this really visual update UI
         OpenedWindow.Dispatcher.Invoke(() => OpenedWindow.IsEnabled = false);
         Thread.Sleep(1000);
         OpenedWindow.Dispatcher.Invoke(() => OpenedWindow.IsEnabled = true);

         //But if I use only one Invoke block, UI not visual update.. Why? In WinForm this work with no problem
         //OpenedWindow.Dispatcher.Invoke(() =>
         //{
         //    OpenedWindow.IsEnabled = false
         //    Thread.Sleep(1000);
         //    OpenedWindow.IsEnabled = true
         //});
     }
     else
     {
         //This not work in WPF. Window seems to stay in enabled state ever
         OpenedWindow.IsEnabled = false;
         Thread.Sleep(1000);
         OpenedWindow.IsEnabled = true;
     }
}

In WinForm all comment statements work well and update UI. In WPF not happens. And I would like to understand why and why setting IsEnabled to false and then to true without invoke, task, ecc..., not really update UI in WPF. Thanks