Bovine bone is real bone, that the body will eventually consume and replace granted it will take up to 7 years for that to happen. It also makes great broth. There is a possibility of an immune response to proteins in the bone, though they try to remove soft tissue and I think it's rare.
HA is a mineral found in large quantities in bone. The blocks are biocompatible and osteoconductive so bone grows through it. It is, however, not bone and will never be replaced by bone. The difference may seem small but remember that the facial skeleton changes slowly as we age and there's no way to predict how it will change with it. That is, it won't change but it's unclear how much of a problem it'll be. Foreign body reactions are possible with HA too, unclear if it happens.