documentation of delivery_type and webhoook_url

I don't get the point of

```
BODYJSONFILE
Path to a file in JSON format with the information to create a new Event Registration.
The JSON should follow the following format:
{
"name": "",
"description": "",
"delivery_type": "WEBHOOK|WEBHOOK_BATCH|JOURNAL",
"webhook_url": ""
"events_of_interest": [{
"provider_id": ""
"event_code": ""
}, { <...more events> }]
}
```

1) When I choose "JOURNAL" is "webhoook_url" optional (if so.. please document)
2) I thought that each provider registration implicitly creates a Journal. Where is the point in creating a Journal Event Registration?