How do you prevent two Payment Request Reviewer Role personnel from updating the same request at the

How do you prevent two Payment Request Reviewer Role personnel from updating the same request at the same time?  I expect the Payment Requests for Review page to include some multi-user functions - did I miss a configuration?  

PeopleSoft Image 29, PeopleTools 8.56

Our testing

1. Configure a Payment Request Template with "Review before Workflow Approval" selected.

2. Create a Payment Request

3. Open Payment Request with one AP reviewer (We'll call them AP Reviewer 1) using the AP WorkCenter's "Payment Requests for Review" page.

4. Open Payment Request with a different AP reviewer (We'll call them AP Reviewer 2) using the AP WorkCenter's "Payment Requests for Review" page.