Event relationships aren't displayed on the Relationships page, just the Events one. If an artist only has event rels, that tab just appears fully blank and empty, without even the header (if there are no rels at all, it says something like:

"Relationships
ArtistX has no relationships.")

Options: either display the event rels there too (we display the work ones even though they have their own page as well) or add a different sentence like "ArtistX has only event relationships" and show the header and that.