Something is "carnivorous" if it directly consumes the flesh (or other parts) of an animal - usually a living one that it kills (as we have a different name for those that consume only already dead animals - necrophages).

Feeding on nutrients from an animal that died and was then broken down by other beings into base elements in the same area as your roots doesn't qualify these trees in any way as either "carnivorous" nor even "necrophage". Carnivorous plants are those that trap and kill animals that they then directly digest, such as a venus fly trap. Those don't just benefit from animals dying around them and being consumed by bacteria - they have mechanisms that cause the death of the animal and then secrete substances that directly convert the animal into plant nutrients.