Immolation.. etc

I recall reading in the forums about when an A-P gets the last hit on someone their weapon can get empowered, whether they strike them, or their poison effect that they initated/etc.. Why is the same not true for Immolation? If you immolate someone and they die from it, you get no experience, you cannot even carve the corpse for a trophy. In that same regard it also makes me question, if I kill someone via immolation, do I get the kill or is it just one of those null kills as if via a mob death but with no xp loss? So is it by design that immolation deaths give no right to the immolater (carve/etc) ?