Spark Group width=100% binding works only if its container width gets bigger

SDK used : 4.0.0.13875

Steps to reproduce:
1. Create an application with the following code:
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/halo"
width="100%"
height="100%"
>

<s:HGroup id="outsideHGroup" width="200">
<s:HGroup id="insideHGroup" width="100%">
<s:Button label="insideHGroup.width =

" />
</s:HGroup>
</s:HGroup>

<s:HGroup top="30" width="100%">
<s:Button label="outsideHGroup.width = 200" click="outsideHGroup.width=200" />
<s:Button label="outsideHGroup.width = 300" click="outsideHGroup.width=300" />
</s:HGroup>

</s:Application>

2. Launch it and click on "outsideHGroup.width = 300" button, and then on "outsideHGroup.width = 200" button

Actual Results:
insideHGroup.width is correctly set to 300 when the "300" button is clicked, but it is not set to 200 when the "200" button is clicked.

Expected Results:
insideHGroup.width should always be the same as outsideHGroup.width because its width is set to 100%.

Workaround (if any):