Why separate svg extension in webpack-isomorphic-tools config?

In [the config](https://github.com/erikras/react-redux-universal-hot-example/blob/master/webpack/webpack-isomorphic-tools.js), you can see that `svg` is configured separately in the `assets`:
```
svg: {
extension: 'svg',
parser: WebpackIsomorphicToolsPlugin.url_loader_parser
},
```
Why is that? When I added it to the `images` `extensions`, the app still seemed to load fine:
```
assets: {
images: {
extensions: [
'jpeg',
'jpg',
'png',
'svg',
'gif'
],
parser: WebpackIsomorphicToolsPlugin.url_loader_parser
```