Web Usability: Are self referentiell links in a navigation bar harmful – and if so, why?

The most CMS produce by default a navigation bar, where the current entry contains the link to the page which is actually open.

When you look at the Web Usability: is that practice harmful - and if so, why? Are there studies which can prove that?

Code example:

<nav>...<li aria-current="page"><a href="/lorem">Lorem</a></li>...</nav>

versus:

<nav>...<li aria-current="page"><strong>Lorem</strong></li>...</nav>

Thanks for your advice.