ember-flatpickr attributeBindings bug

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  onFlatpickrChange(dates) {
    this.set('flatpickrValue', dates);
  },
  flatpickrValue: new Date(),
});

templates.application.hbs

<h1>ember-flatpickr attributeBindings bug</h1>

<br>
Initial date value is formatted correctly by flatpickr.
<br>
Choose a new date.
<br>
ember-flatpickr will override the formatted string flatpickr creates.
<br>

{{ember-flatpickr
  allowInput=true
  dateFormat="Y-m-d"
  onChange=(action onFlatpickrChange)
  value=(readonly flatpickrValue)
}}

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",
    "ember-flatpickr": "1.1.7"
  }
}