Very interesting! Does that NavController let you push things to it? Usually NavController providers are instantiated because somewhere there is an ancestor component that extends NavController, like a Nav or a Tab or Tabs.
Conceptually I'm not sure how a NavController that isn't associated with some sort of component would work, because where are things being pushed to?
From a technical standpoint, I'm not sure how that could be working, because it doesn't look like NavController is Injectable (in the beta.2 or in alpha.53), so angular would have no way of knowing to provide its dependencies.
Also, NavController has an ElementRef as part of its constructor, which I would think would fail if it were in the providers array and not coming from a component.
But! I believe you that the code is working, so I'm genuinely curious what's going on here. What is your use case? If it's related, could you weigh in on https://github.com/driftyco/ionic/issues/5543? Navigation is something where I think we want to better understand how people expect it to be working, so we make sure it's easy to do or document the common points of confusion really well. Thanks!