[mattnewton]

The first time it was for a sub-route that could be brought up in any other route (to show a little search pane in the app). We were told by the community just "not to do that" but it was in our spec and there wasn't a way to load the same countroller for multiple routes. The second time was more short lived, but it was to allow asynchronous modules to be loaded after the main app. There were no community solutions to this at the time. The last time wasn't really forking ember but we underwent a painful process of remaking most of our views in vanilla JavaScript for performance on mobile, which has gotten completely out of hand with all the two way bindings of pre-glimmer ember. It felt like we were fighting the framework the whole time.

If you go off the rails, it is extremely painful. I haven't looked at Ember in a while, because of my experiences, so ymmv. It could all be completely different now.