TabView.TabItems: why IList<object>?

[DanielTrommel]

Background: developing code that tries to work out the instance properties of a given XAML element via reflection, and had some trouble with TabView's content property TabItems.

The TabView class projected runtime class ITabView indicates TabItems to be of type IList<object>.
Why is the broad object chosen, and not the seemingly (functionally) required TabViewItem?

Btw, I tested whether the IList<object> indeed meant I could just put in `anything':

• Works for a single button

       <TabView>
           <Button Content="Click me!"/>
       </TabView>
  

• Crashes the application when I provide two buttons:

          <TabView>
              <Button Content="Click me!"/>
              <Button Content="Click me!"/>
          </TabView>
  

For comparison, for (Stack)Panel, the ContentProperty Children is a UIElementCollection, which makes sense, as any UIElement derivative can be put in.

Questions:

1. Why is TabView's TabItems not more restricted?
2. Is there some documentation/conventions around this to understand what is and isn't allowed to be assigned?
3. Is the two-buttons-scenario a trivial misstake on my part, or is the crash something I should report?