Ember component: variable set before init?

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  message: null,
  
  name: Ember.computed('message', {
    set(_key, value) {
      let message = `${this.get('greeting')} ${value}`;
      this.set('message', message);
    }
  }),
  
  init() {
    this._super(...arguments);
    this.set('greeting', 'hello ');
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

{{my-component name="David"}}

templates.components.my-component.hbs

<h2>My Component</h2>

Message: {{message}}

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"
  }
}