angle bracket splattributes vs attrs

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: '',
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>

<style>
.oh-hai {
background: lightblue;
}
.my-comp {
text-transform: uppercase;
}
</style>


<MyComponent class="oh-hai" />

templates.components.my-component.hbs

<div ...attributes class="my-comp">
	<p><code>.oh-hai</code> makes stuff <code>background: lightblue</code></p>

	<p><code>.my-comp</code> is supposed to be uppercase</p>

	<p>as long as <code>class="oh-hai"</code> is passed to MyComponent, it loses its own internal class?</p>
</div>

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"
  }
}