Horizontally aligning elements in a TileLayout doesn't work when the container only has a couple items

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"
width="100%">

<s:TileGroup width="100%" horizontalAlign="center" columnAlign="justifyUsingWidth">
<s:Button label="Hello" />
<s:Button label="Hello" />
</s:TileGroup>

</s:Application>

2.
3.

Actual Results:

The two buttons seem to be aligned to the left of the application.

Resizing the width of the app causes the buttons to jump around.

Expected Results:

The two buttons should be horizontally aligned in the middle of the application.

Workaround (if any):

Set requestedColumnCount="2" on the layout.