Of the three sources of class-stacking, only Sphinx Ordainer specifically omits spells from its effects. However, any combination of Carrion Cockatrice, Forest Pact, and Summon Horde still results in as-many minions as non-stacked class members. I’m not sure which way is the intended behavior but this seems inconsistent with the latter creature’s and perk’s wordings.
For good measure I trait launched Carrion Cockatrice to a party I was casting Holy Shock against which also resulted in as-many casts as non-stacked class members on their side. I’m not certain of another potentially valid spell to test with besides Demonic Strike; which both also counts the target’s party and has a harder condition to observe.