Nameless Seer not spawning with Rare>Boss Scarab

Hey if you use the scarab that deletes rare monsters for map bosses with a 15% chance and roll the nameless seer and for some reason the pack gets converted into a boss then you dont spawn a nameless seer in the map if you rolled him in your lantern.
atleast thats my assumption since that did happen to me today, tought the bugs were fixed but that were the conditions in my map atleast