Sorry for the delay, I think I can see why the notify flags aren’t set up correctly. In UDestructibleComponent::OnCreatePhysicsState there’s a call to CreateShapeFilterData which sets up the filter flags. We pass bEnableImpactDamage as the parameter for enabling the notify flag. A quick way to test would be to enable impact damage on your mesh and see if you’re getting more event callbacks.
If this works then you’ll need to change the flag passed to CreateShapeFilterData and possibly make a change to the code which catches the impact damage events if you don’t want that to be enabled (UDestructibleComponent::ApplyDamage and UDestructibleComponent::ApplyRadiusDamage)