Destructive play bug

Why is it that running an elder guardian defiled cathedral with destructive play which is already witnessed doesn't spawn extra bosses?
Running elder guardian doesn't counts towards regular map witness anyway since you don't kill the regular map bosses, only when it is an elderslayer so maven should spawn extra bosses on the 3rd round of the elder guardian fight.

Because Maven only witnesses a boss one time and then gets bored. You have to do sets of 4 different Guardians + invitation then repeat if you want the extra bosses. Has always worked this way since Maven was added. I find it easier to just stockpile boss maps until I have 4 different Guardian maps (or Horizon Orb shaper maps). Run all 4, invitation, do it again if I have more or go back to regular map witnessing to stockpile.