Computed property chain makes prop unenumerable

controllers.application.js

import { later } from '@ember/runloop';
import Ember from 'ember';
import { getOwner } from '@ember/application';
import EmberObject, { computed } from '@ember/object';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  init() {
    const owner = getOwner(this);
    const factory = owner.factoryFor('model:test');
    const instance = factory.create();
    this.set('instance', instance);
    
    later(() => {
      // this.get('someProp');
    	console.log(instance, instance.someProp);
    	console.log(Object.getOwnPropertyDescriptor(instance, 'someProp'));
    
    	for (let key in instance) { console.log(key); }
    }, 1000);
  },
  
  someProp: computed('instance.someProp', function () {
   return `test ${this.get('instance.someProp')}`; 
  }),
});

models.test.js

import EmberObject from '@ember/object';

export default EmberObject.extend({
  someProp: 'someValue',
});

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"
  }
}