apache airflow ExternalTaskMarker clear another dag's task recursively but task state is None

i'm testing ExternalTaskSensor and ExternalTaskMarker. ExternalTaskSensor wait until external Dag's Task finished and ExternalTaskMarker clear another dag's task recursively.

https://airflow.apache.org/docs/apache-airflow/stable/howto/operator/external_task_sensor.html

this is my parent dag

# parent_dag.py

from datetime import datetime, timedelta

from airflow.sensors.external_task import ExternalTaskMarker
from airflow.operators.bash import BashOperator

from airflow import DAG

default_args = {
    "owner": "admin",
    "retries": 0,
    "depends_on_past": False,
    "retry_delay": timedelta(minutes=2),
}

dag = DAG(
    dag_id='parent_dag',
    default_args=default_args,
    start_date=datetime(2022, 1, 1, 9, 00, 0),
    schedule_interval='@daily',
    catchup=True
)

task_1 = BashOperator(
    task_id='echo_hello',
    bash_command='echo HELLO!!!!',
    dag=dag,

)

task_2 = ExternalTaskMarker(
    task_id='parent_trigger',
    external_dag_id='child_dag',
    external_task_id='receive_call',
    dag=dag
)

task_1 >> task_2

and child dag

# child_dag.py

from datetime import datetime, timedelta

from airflow.sensors.external_task import ExternalTaskMarker, ExternalTaskSensor
from airflow.operators.bash import BashOperator

from airflow import DAG

default_args = {
    "owner": "admin",
    "retries": 0,
    "depends_on_past": False,
    "retry_delay": timedelta(minutes=2)
}

dag = DAG(
    dag_id='child_dag',
    default_args=default_args,
    start_date=datetime(2022, 1, 1, 9, 00, 0),
    schedule_interval='@daily',
    catchup=True
)

receive_call = ExternalTaskSensor(
    task_id='receive_call',
    external_dag_id='parent_dag',
    external_task_id='parent_trigger',
    dag=dag
)

task_1 = BashOperator(
    task_id='echo_hello',
    bash_command='echo HELLO!!!!',
    dag=dag
)

receive_call >> task_1

Sensor work but Marker doesn't work as i expected.

when i clear parent dag's with ExternalTaskMarker, child dag change to None state. i expected child dag will be clear and rescheduled.

do i missunderstanding about ExternalTaskSensor and ExternalTaskMarker?