Computed Keyed on Nested Pojo Array

controllers.application.js

import Ember from 'ember';
import { A } from '@ember/array';
import { computed } from '@ember/object';

export default Ember.Controller.extend({
  init() {
    this._super(...arguments);
		this.pojoProp = {
    	features: new A([]),
  	};
  },
  appName: 'Ember Twiddle',
  computedFromNested: computed('pojoProp.features.[]', function() {
    console.log('recomputes');
    return this.get('pojoProp.features.length');
  }),
  actions: {
    pushToNestedProp() {
      this.get('pojoProp.features').pushObject('grape');
    }
  },
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
Why doesn't "0" this recompute? ->
{{computedFromNested}}

<button onclick={{action 'pushToNestedProp'}}>
	Add
</button>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}