FB Instant Articles related articles section

Question

Facebook's documentation for instant articles states that for "related articles" if we leave off the list of related articles, Facebook will automatically select 4 articles for us. I am not seeing this behavior. Instead, I get the error: Related Articles Block is Empty. Has anyone come across this?

The tag that I current have is as below:

<footer>
  <ul class="op-related-articles">
  </ul>
</footer>

Answer 1

You can include a maximum of four links in this list. Unlike in the footer, Facebook will not automatically populate the remaining links if you include fewer than four.

Answer 2

This is not actually the case.

I tried the same thing after reading the FB documentation, I thought facebook will get pages randomly but they don't.