Subscribing to firebase topic do not filter push message

Question

Context

I am developping an Angular web application using firebase messaging. I configured firebase successfully (I guess) and I now subscribe to a "users" topic.
To do so I use the subscribeToTopic('users') from 'firebase-admin' library on server side (NestJS application) and it always prints the success message.

await firebaseAdmin
      .messaging()
      .subscribeToTopic(firebaseIdToken, topic)
      .then((response) => {
        console.log('Successfully subscribed to topic:', response);
        response.errors.forEach((err) => console.log(err.error));
      })
      .catch((error) => {
        console.log('Error subscribing to topic:', error);
      });

On client side, I use AngularFireMessaging.messages to listen the message push.
To test the push message, I use postman and the firebase api https://fcm.googleapis.com/fcm/send with following body

{
    "topic": "users",
    "notification": {
        "title": "notif title",
        "body": "Hello world"
    },
    "data": {
        "action": "CREATE",
    },
    "to": "{{firebase.id_token}}"
}

where firebase.id_token is the id token generated by firebase with AngularFireMessaging.getToken function
I successfully receive the push message on my client app.

Issue 1

But now, if I change the "topic" key in the request body by any topic name, I still receive the push messages on client side !! And this is not what I expected I wonder what I'm doing wrong with the subscription or configuration making the client side not filtering the push messages according to topic subscription.

Issue 2

I tryied to implement my own sendPush method on server side with the following code

@Post('send-push')
async sendPushMessage(@Body() { topic, payload }: FirebasePush): Promise<void> {
    console.log('sendPushMessage', topic, payload); // print the right values
    await firebaseAdmin
             .messaging()
             .sendToTopic(topic, payload)
             .then((response) => {
                 console.log('Successfully sent message:', response); // this is printed with the message id
             })
             .catch((error) => {
                 console.log('Error sending message:', error);
             });

}

if I call this endpoint with postman using the following body

{
    "topic": "users",
    "payload": {
        "data": {
            "action": "CREATE",
        }
    }
}

the message seems to be send correctly because the message id is printed in the console but I never receive any message push on client side and I wonder why as well
I hope someone can help me with theses issues, thanks