How to create a Hiring Manager role for creating requisition for their BU?

Summary:

The recruirement is simple: Restrict Hiring Manager to create requisition only for the BU they are tagged to. However, we are unable to achieve this.

Steps performed:

1. Created Organization Tree: Enterprise 1 > BU 1, BU 2, BU 3, BU 4
2. Update the same organization in Enterprise Recruiting and Candidate Experience Information
3. Create custom Organization security profile:
   1. Organization Hierarchy: Generic Organization Hierarchy > Organization Tree > Organzation tree name
   2. Top Organization selection: Organization = Enterprise 1
   3. Organization Classification = Business Unit
4. Add the custom organization security profile to the Organization profile within the role

Also, we have flattend the tree. We still see all the BU's while creating requisiton.

Content (please ensure you mask any confidential information):