grunt: cdnify doesn't do anything - gruntjs

Question

I have created an AngularJS application using Yeoman. It also uses the cdnify task that shoud transform bower_components/angular/angular.js into //ajax.googleapis.com/ajax/libs/angularjs/1.2.15/angular.min.js. The generated index.html contains the following code:
<!-- build:js scripts/vendor.js -->
<!-- bower:js -->
<script src="bower_components/jquery/dist/jquery.js"></script>
<script src="bower_components/angular/angular.js"></script>
<script src="bower_components/bootstrap-sass-official/vendor/assets/javascripts/bootstrap.js"></script>
<!-- endbower -->
<!-- endbuild -->
There is also a task that combines, minifies and uglifies all the scripts, so these scripts are combined into a single vendor.js file. To avoid jquery.js and angular.js to be included in this process, I changed it into:
<script src="bower_components/jquery/dist/jquery.js"></script>
<script src="bower_components/angular/angular.js"></script>
<!-- build:js scripts/vendor.js -->
<!-- bower:js -->
<script src="bower_components/bootstrap-sass-official/vendor/assets/javascripts/bootstrap.js"></script>
<!-- endbower -->
<!-- endbuild -->
When I run grunt serve:dist the cdnify task is ran and generates the following output:
Running "cdnify:dist" (cdnify) task
Going through dist/404.html, dist/index.html to update script refs
My bower.json looks like this:
{
"name": "myAmazingAngularApp",
"version": "0.0.0",
"dependencies": {
"jquery": "~1.11.0",
"angular": "1.2.x",
"bootstrap": "~3.1.1",
"angular-bootstrap": "~0.10.0"
}
}
Does anyone know what I am doing wrong? I would think it should work out-of-the-box, so I suspect it's a bug...
There is also a .bowerrc file that has the following content:
{
"directory": "app/bower_components"
}
I tried changing this setting to "directory: bower_components" when running grunt cdnify, but it doesn't help.