Parent Event Stops Propagation of Child Action

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  logs: [],
  
  actions: {
    log(line) {
      this.get('logs').pushObject(line);
    },
    
    stopPropagation(event) {
      this.get('logs').pushObject('This event stops propagation');
      event.stopPropagation();
    }
  }
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
  
  --padding-xsmall: 4px;
  --padding-small: 8px;
  --padding-medium: 16px;
  --padding-large: 32px;
  
  --color-text: #F1EFF3;
  --color-light: #6C5084;
  --color-medium: #350F57;
  --color-dark: #140620;
}

.parent {
  padding: var(--padding-medium);
  margin: var(--padding-large) 0;
  max-width: 400px;
  color: var(--color-text);
  background-color: var(--color-medium);
  border: 1px solid var(--color-dark);
}

.child {
  padding: var(--padding-small);
  margin: var(--padding-small) 0;
  cursor: pointer;
  background-color: var(--color-light);
  border: 1px solid var(--color-dark);
}

templates.application.hbs

<div class="parent" onclick={{action "stopPropagation"}}>
  Parent that stops propgation onclick

  <div class="child" {{action "log" "child"}}>Child (will never fire its Ember action)</div>
</div>

<div class="parent" onclick={{action "log" "parent"}}>
  Parent that does <strong>not</strong> stop propgation onclick

  <div class="child" {{action "log" "child"}}>Child (will fire after parent)</div>
</div>

Events:
<ol>
  {{#each logs as |log|}}
    <li>{{log}}</li>
  {{/each}}
</ol>

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"
  }
}