Custom elements have their purpose, but in most cases you don't need them and existing elements suffice.

With how this article was written (the use of "then" when they meant "than", mentioning "article-heading" when that is not in their previous example, but rather "article-header") makes me believe this didn't get much thought on the topic they wrote about, but rather wrote up a quick post.

Additionally, the problems that they bring up can be mitigated with the use of BEM structure for their class names.