Pretender chassis and things with effect 0x1e0 (I theorise this is #indepspells the mod command) use their own logic that gets spells up to a given research level. For pretender chassis, this is 7. Everything else seems to be hardcoded to chassis.
I'm not sure what lets other throne defenders cast things like Horde of Skeletons or make big elementals.
This list is manual and may miss some possible things included above. Technically it will apply to ANYTHING with ID 1-343.
Likely