Nested Computed Properties Bug

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  init() {
    this.set('firstSubObject', this.get('dummy.tiers.firstObject.subObject'));
    console.log(this.get('dummy.tiers.firstObject.subObject'));
  },
  
  dummy: Ember.Object.create({    
    tiers: [
    	Ember.Object.create({
      	subObject: Ember.Object.create({
        	value: 3
      	})
      }),
      Ember.Object.create({
        subObject: Ember.Object.create({
        	value: 5
      	})
      }),
      Ember.Object.create({
      	subObject: Ember.Object.create({
        	value: 7
      	})
      })
    ]
  }),
  
  tierSubObjects: Ember.computed('dummy.tiers.@each.subObject', function () {
  	return this.get('dummy.tiers').map(tier => {
      return tier.get('subObject');
    });
  }),
  
  subObjectValuesList: Ember.computed('tierSubObjects.@each.value', 'dummy.tiers.@each.subObject', function () {
    this.get('tierSubObjects');//get dependany computed property to make sure it is accessed
    return this.get('dummy.tiers').map(tier => {
      return tier.get('subObject.value');
    });
  }),
  
  listToDisplay: Ember.computed('subObjectValuesList', function() {
    return this.get('subObjectValuesList');
  }),
  
  actions: {
   	incrementFirstValue() {
      let subObject = this.get('firstSubObject');
      subObject.set('value', subObject.get('value') + 1);
    },
    addNewTier() {
     	this.get('dummy.tiers').addObject(
        Ember.Object.create({
      	subObject: Ember.Object.create({
        	value: 9
      	})
      }),
      );
    }
  }
});

templates.application.hbs

<h1>List of Values from Sub-Objects</h1>
<br>
{{listToDisplay}}
<br><br>
<button {{action "incrementFirstValue"}}>Increment First Value</button>
<br>
<button {{action "addNewTier"}}>Add New Tier</button>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}