Hello Heather Singleton,
Thanks for posting your question in the Microsoft Q&A forum.
Microsoft Entra access reviews currently cannot send notifications only to managers while suppressing emails to group members. The Email notifications toggle only controls emails to reviewers and admins, Entra will still automatically email the users whose access is being reviewed, and this behavior cannot be disabled separately.
The only practical workaround is to turn off Email notifications in the access review and then notify the managers yourself through an external method. This avoids sending emails to members, although it requires handling manager notifications outside of the built-in Entra system.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful