why UE4 not using PhysX's eTRIGGER_SHAPE as Trigger?

as far as i know, UE4’s Trigger is implemented by overlapping the component with the scene, and this check is driven by a recursive UPrimitiveComponent::UpdateOverlaps, this may cost some CPU for very deep transform hierarchy.
i wander why not using PxShapeFlag::eTRIGGER_SHAPE for Trigger, a feature already implemented by PhysX, what’s the ration beind the choice?