Celery get result from other client

for example, I have this app:

from celery import Celery, Task

class Config:
    broker_url = 'pyamqp://guest@192.168.88.82/'
    enable_utc = True
    task_track_started = True
    result_backend = 'rpc://'
    include = ['proj.tasks']
        
app = Celery()
app.config_from_object(Config)

and tasks:

    @app.task(bind=True)
    def add(self,x,y):
        # print(self.request.id)
        for i in range(10):
            i += 1
            sleep(15)
            self.update_state(state="PROGRESS", meta={'progress': 10*i})
        return (x + y)

then I start the client in python shell to run the task:

from proj import add    
r = add.delay(1,1)
r.task_id # get 'bb2b9676-b9ea-4fc0-a45a-75f796217208'

in the same client, I can do the following and get the status and result:

from celery.result import AsyncResult
rid = AsyncResult('bb2b9676-b9ea-4fc0-a45a-75f796217208')
rid.status # get 'PROGRESS' or 'SUCCESS'

in another client (another python shell) I do the same, but I get wrong result:

from celery.result import AsyncResult
rid = AsyncResult('bb2b9676-b9ea-4fc0-a45a-75f796217208')
rid.status # get 'PENDING'

What is happening? I do not understand.