"When task is completed" Notification not received

Summary:

Notification to HR not received when Pending Worker completes their Preboarding Journey's tasks.

Content (please ensure you mask any confidential information):

In our Journeys configuration, Task configuration - Notifications tab, we're using the "When task is completed" setup, to notify the owner of the task (checkbox), using the Content Type "Default Content".
Owner of the task is set to Area of Responsibility (AoR), scope of the AoR is the whole Legal Employer when assigning the AoR to an HR employee.

But HR employee with AoR assigned is not receiving anything.

On the other hand, the notification "When task is assigned or reassigned" to the Performer (the Pending Worker) is received as expected.