It's explained in game why they added King to the Titania title. While the first Titania was fighting the Light Warden, during the fight those Fae that remembered Voeburt, while witnessing the fight, had seen flashes of the Voeburt's King in the way Titania fought to protect them from the Light Warden. So after they sealed her in the palace they added King to her title in remembrance to Voeburt and to honor her sacrifice.