The "Only notify requested team members" setting can now be enabled independently of "Enable auto assignment" in the Team's code review settings.
This is useful in scenarios where many users are auto assigned but not all users require notification. For example, when repositories are configured with teams as code owners but contributors know the specific individual to review their pull request. This setting now allows you to require that team for review, but without always notifying the whole team unnecessarily.
Read more about managing code review settings for your team.