Ember loading substate not working from addon

I have an Ember addon that is npm linked with a project.

If I create the file app/pods/application-loading/template.hbs in the addon, the loading HTML is not rendered from the base-project. However, if I create the exact same file in the base-project itself, the loading HTML is rendered.

My understanding is that the addon's app folder should be merged with the base-application's app folder, so this shouldn't be possible. What's going on?