It changes the artist credit name on the page, not the kind of relationship. So if you tick the box, change the name to Vinnie and hit Done, all credits will be renamed Vinnie. If you change the relationship to vocals, nothing will change (except the one relationship you are editing, of course).
I agree that the description isn’t clear on this at all. Something like “Change the name for Vinnie Colaiuta in all relationships on this page.” would be better I think.