Safestring vs. inside template vs js

controllers.application.js

import Ember from 'ember';
import { htmlSafe } from '@ember/template';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  wordFromAbove: 'Bird is the word',
  
  safeWord: htmlSafe('Roger that')
});

helpers.my-helper.js

import Ember from 'ember';
import { isHTMLSafe } from '@ember/template';

export function myHelper([key]/*, hash*/) {
  console.log(key);
  const isSafeString = isHTMLSafe(key);
  const keyType = typeof key;
  return `[${keyType}] [safe:${isSafeString}] ${key}`;
}

export default Ember.Helper.helper(myHelper);

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

section {
  margin: 20px;
  padding: 20px;
  background-color: hsl(0,0%,90%);
}

templates.application.hbs

<h1>Helper check string type</h1>
<br>
<br>
<section>
 {{my-helper 'Word on the street is...'}}
</section>
<section>
 {{my-helper wordFromAbove}}
</section>
<section>
 {{my-helper safeWord}}
</section>
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}