specific Eldritch altar does not work with Domination scarab of Terrors

The Eldritch altar mod "Final map boss drops 4 additional ambush scarabs" does not proc from the additional map bosses summoned by Domination scarab of Terrors.

My additional map bosses are dropping all of the other "Final boss drops XXXX" items correctly, but this specific mod is definitely not working. Specifically, I currently have "3 additional chaos orbs" and "4 additional orbs of unmaking".

I am also running this in a memory tear thread map with inherent "Final map boss drops 3 additional scarabs" from the tear thread altars, maybe there's some interaction going on between the two mods.

UPDATE: The mod triggered on the actual final boss of the map.
The map in question was Overgrown Shrine.

Update on the update: In the very next thread the same thing is happening with "map boss drops additional legion scarabs" and cartography scarabs. I suspect there might be an unwanted interaction between the memory thread altar mod and the specific scarab mods from eldritch altars