computed property testing

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle'
}); 

var Item = Ember.Object.extend({
  value: 0,
  hasValue: Ember.computed.gte("value", 1)
});

var ItemList = Ember.Object.extend({
  items: [],
  itemsWithValue: Ember.computed.filterBy("items", "hasValue", true),
  anyHaveValue: Ember.computed.notEmpty("itemsWithValue"),
  
  showState: function() {
    // Comment out the next line, and things start to work properly
    console.log("anyHaveValue: " + this.get("anyHaveValue"));
  }.observes("anyHaveValue")

});

var row = ItemList.create();
row.get("items").pushObject(Item.create());
console.log(row.get("anyHaveValue")); // false, none of them do

row.get("items")[0].set("value", 1);
console.log(row.get("anyHaveValue")); // true

row.get("items")[0].set("value", 2); 
console.log(row.get("anyHaveValue")); // should still be true, but if we have the console.log() line in the observes() function, it now shows incorrectly as false

row.get("items")[0].set("value", 3); 
console.log(row.get("anyHaveValue")); // should still be true, but remains broken 

application.template.hbs

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

twiddle.json

{
  "version": "0.4.10",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.11/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember-template-compiler.js"
  }
}