Kulemaks Invitation

Is it inteden by GGG to not be able to farm these? When you kill the vessel, portal out, grab a new invitation and then jump in again its the same instance. Meaning no new boss, just the leftover loot still there. And creating a new instance to the well of souls doesnt seem to reset the boss fight instance.

All I wanna know is if its inteded or just a bug.

Thanks GGG beforehand if you give me an answer, im sure other are also wondering about this.