Ember 3 conditional statement

Why while this code does render,

<ol>
  
    <li ></li>
  
</ol>

<ul>
  
    <li ></li>
  
</ul>

this does not?

}
  
    <li ></li>
  
}

The last snippet emits <ol></ol> before the list and no closing tag after the list:

<div id="ember260" class="ember-view"><h2>Ordered List Of Things</h2>
<ol></ol>
    <li data-ember-action="" data-ember-action-261="261">yarn</li>
    <li data-ember-action="" data-ember-action-262="262">feathers</li>
    <li data-ember-action="" data-ember-action-263="263">dinner plate</li>
    <li data-ember-action="" data-ember-action-264="264">sheep</li>
</div>

and why does this code not even compile?

<ol>

<ul>

  
    <li ></li>
  

</ol>

</ul>

Error:

Unclosed element ol (on line 2).