Custom HR role not able to restrict BU- LOV for adding new person (Employee, POI, Pending worker)

Summary:

We have a custom HR role to add new person - all 3 types -hire employee, add pending workers, add a non-worker. We want to restrict the LOV for Business unit to the Business Unit assigned to the login user. For example, the dropdown should only display the business unit assigned to user by AOR.
We tried to test this with the organization security profile value set to only one BU, but it does not work as expected.
Please help with the resolution. Screenshot shared is for hire an employee, but the same issue applies to add a non-worker and add pending worker.