Using relations allows the use of functionalities, for example the "related content block". Relating on author is one of the requirements for this block. Updating all these functionalities to also support an author is complex and would cost a lot of code to maintain. Using a hidden relation is a better way.
Add a hidden relation, type = author, for authors.
.Notificatie oplevering gestuurd naar Integrated Marijn (firstname.lastname@example.org)