groupName doesn't work in DataGroup renderers

Steps to reproduce:
1. Compile and run:

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark">

<s:DataGroup>
<s:layout>
<s:VerticalLayout />
</s:layout>
<s:dataProvider>
<s:ArrayList>
<fx:String>one</fx:String>
<fx:String>two</fx:String>
<fx:String>three</fx:String>
<fx:String>four</fx:String>
</s:ArrayList>
</s:dataProvider>
<s:itemRenderer>
<fx:Component>
<s:ItemRenderer>
<s:RadioButton label="

" groupName="rendererGroup" />
</s:ItemRenderer>
</fx:Component>
</s:itemRenderer>
</s:DataGroup>
</s:Application>

2. Select the different radio buttons
3.

Actual Results:

Each radio button is selectable

Expected Results:

Only one radio button should be selectable at a time.

Workaround (if any):

Define a RadioButtonGroup in the application and point each RadioButton to it via group="

"