What is the latest with initialization and deferReadiness()?

BTW, what does this mean, from the docs: “However, if the setup requires a loading UI, it might be better to use the router for this purpose.”?

As far as I can tell, deferReadiness isn’t working for me. In fact, even though I have logging code all over my app, the very first thing I see in the log is "Transitioned into ‘index’ ". This is my relevant code:

  App = Ember.Application.create({
    , rootElement: "body"

What concerns me is that it is also, seemingly, only supposed to work prior to initialization of the app. What if I want to hold off routing later in the day? For instance, if I’m loading a template for a view. Is there a place for that?

    @method deferReadiness
  deferReadiness: function() {
    Ember.assert("You cannot defer readiness since the `ready()` hook has already been called.", this._readinessDeferrals > 0);

    @method advanceReadiness
    @see {Ember.Application#deferReadiness}
  advanceReadiness: function() {

    if (this._readinessDeferrals === 0) {
      Ember.run.once(this, this.didBecomeReady);