microsoft-ui-xaml VisualTreeHelper unable to traverse TeachingTip content

Describe the bug

I am doing some customization using attached DependencyProperty, so I attached a Loaded event handler to a TeachingTip to traverse it with VisualTreeHelper, but it is unable to traverse the visual tree of it, giving no useful information.

Why is this important?

This should work

Steps to reproduce the bug

I have a TeachingTip defined in xaml

        <Button x:Name="Button" Click="Button_Click">Click to open tip</Button>
        <TeachingTip
            x:Name="MyTip"
            Loaded="MyTip_Loaded"
            LayoutUpdated="MyTip_LayoutUpdated"
            Content="Some tip"/>

Add a helper function to traverse a control and print it type name and name

static void printVisualTree(winrt::Microsoft::UI::Xaml::FrameworkElement const& element)
{
	if (!element)
		return;

	OutputDebugString(std::format(L"{}: {}\n", winrt::get_class_name(element), element.Name()).data());

	auto const numChild = winrt::Microsoft::UI::Xaml::Media::VisualTreeHelper::GetChildrenCount(element);
	for (auto i = 0; i < numChild; ++i)
	{
		printVisualTree(winrt::Microsoft::UI::Xaml::Media::VisualTreeHelper::GetChild(element, i).as<winrt::Microsoft::UI::Xaml::FrameworkElement>());
	}
}

Print out the visual tree in both Loaded and LayoutUpdated event

	void MainWindow::MyTip_Loaded(winrt::Windows::Foundation::IInspectable const& sender, winrt::Microsoft::UI::Xaml::RoutedEventArgs const& e)
	{
		auto teachingTip = sender.as<winrt::Microsoft::UI::Xaml::Controls::TeachingTip>();
		OutputDebugString(L"==============Loaded==========\n");
		printVisualTree(teachingTip);
	}

	void MainWindow::MyTip_LayoutUpdated(winrt::Windows::Foundation::IInspectable const& sender, winrt::Windows::Foundation::IInspectable const& e)
	{
		OutputDebugString(L"==============Layout Updated==========\n");
		printVisualTree(MyTip());
	}

Actual behavior

Gives

==============Layout Updated==========
Microsoft.UI.Xaml.Controls.TeachingTip: MyTip
Microsoft.UI.Xaml.Controls.Border: Container
==============Loaded==========
Microsoft.UI.Xaml.Controls.TeachingTip: MyTip
Microsoft.UI.Xaml.Controls.Border: Container