IsEnabledChanged isn't raised for the FrameworkContentElement if the IsEnabled property is changed for the container

In my app at startup, I set the MainWindow.IsEnabled to false.
The BarManager MainMenu and toolbar Bar all look disabled as expected as does the NavBarControl.

After some initialization, I set MainWindow.IsEnabled to true.
Everything then becomes enabled except for the MainMenu and toolbar Bar. Setting IsEnabled=true on these is a workaround but I expected them to inherit the IsEnabled setting. Note that the NavBarControl does inherit correctly.

A quick look at the source code shows this line for the NavBarControl
IsEnabledProperty.OverrideMetadata(typeof(NavBarControl), new FrameworkPropertyMetadata(true, OnIsEnabledChanged));

Should something similar be in place for the BarManager and associated controls?

Steps to Reproduce:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using System.Diagnostics;

namespace WpfApplication38 {

    /// <summary>

    /// Interaction logic for Window1.xaml

    /// </summary>

    public partial class Window1 : Window {

        public Window1() {

            InitializeComponent();

        }

        private void Button_Click(object sender, RoutedEventArgs e) {

            grid.IsEnabled = !grid.IsEnabled;

        }

    }

    public class MyButtonInfo : FrameworkContentElement {

        public MyButtonInfo() {

            IsEnabledChanged += new DependencyPropertyChangedEventHandler(OnIsEnabledChanged);

        }

        void OnIsEnabledChanged(object sender, DependencyPropertyChangedEventArgs e) {

            Trace.WriteLine("IsEnabled = " + IsEnabled.ToString());

        }

    }

    public class MyItemsControl : ItemsControl

          {

               static MyItemsControl()

               {

                    IsEnabledProperty.OverrideMetadata(typeof(MyItemsControl), new FrameworkPropertyMetadata(true, OnIsEnabledChanged));

               }

         protected override bool IsItemItsOwnContainerOverride(object item) {

            return false;

        }

        protected override DependencyObject GetContainerForItemOverride() {

            return new Button();

        }

        protected override void PrepareContainerForItemOverride(DependencyObject element, object item) {

            Button btn = element as Button;

            btn.Content = ((MyButtonInfo)item).Name;

        }

          static void OnIsEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {

               ((MyItemsControl)d).OnIsEnabledChanged();

          }

          void OnIsEnabledChanged() {

               foreach(FrameworkContentElement item in Items)

                    item.CoerceValue(IsEnabledProperty);

         }

    }

}