Why is the non-existent `elasticsearch.url` mentioned in Kibana’s configuration documentation?

Start the Kibana container with the following command:

docker run -p 127.0.0.1:5601:5601 -d --name kibana --network elastic-net \
  -e ELASTICSEARCH_URL=http://elasticsearch:9200 \
  -e ELASTICSEARCH_HOSTS=http://elasticsearch:9200 \
  -e ELASTICSEARCH_USERNAME=kibana_system \
  -e ELASTICSEARCH_PASSWORD=$KIBANA_PASSWORD \
  -e "xpack.security.enabled=false" \
  -e "xpack.license.self_generated.type=trial" \
  docker.elastic.co/kibana/kibana:8.15.0