Error route model with reject from model hook

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'https://github.com/emberjs/ember.js/issues/15842'
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  model () {
    // works if you use actual Error...
    // return Ember.RSVP.reject(new Error('fetching the model failed'))
  	return Ember.RSVP.reject('fetching the model failed'); 
  }
});

templates.application-error.hbs

{{#if model}}
  <h1>{{model}}</h1>
{{else}}
  <h2>Shouldn't it be "fetching the model failed"?</h2>
{{/if}}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}