Possible death bat bug

Ok so wolpertingers cast a spell from a set school agter attack.

A death bats trait gives it a 20% chance to cast necrosis after an ally casts a spell.

I would have thought this would include spells auto cast by wolpertingers, but that doesnt seem to be the case. After about 20 battles with dual wolpers my death bats trait has not procced even once.

Possible bug?

Still not procced after my wolpers attack/cast trait combo.

Havent seen it proc on cast on hit/def etc spells either as yet.