Ember.Object.create set and get

I have a small problem with Ember.Object.create(). In my route in setupController(), I am trying to add new Ember Object to an array. Whenever I enter that route first I do controller.set('onRules',[ ]) so I have an empty array onRules to which I want to add object and then I am creating new Ember object like that:

  controller.get('orRules').addObject(
      Ember.Object.create(
        {
          id: 0,
          isAllowedToDelete: false,
          foo: "bar"
        }
      )
    );

After that the object is being added to the array and when console.log orRules I can see that set and get functions are only available for id and isAllowedToDelete but not for foo. You can see it on following screenshot:

orRules class in console.log Can somebody explain me why Ember decides to make available set and get functions only for two first properties and not for foo ?

Thanks for your help!