At Boston Scientific, when assigning a user (principle) into a Role within a Set-up Participant task, the Team is immediately updated. However, It should not be persisted until task is completed.
User may not complete task at that point. It goes against general principles to persist information prior to completing the task. Boston Scientific does some business rule validations at this point that could render the assignment as not allowed. For example, the same user may not be assigned as the approver to multiple roles.