Is Employee Role mandatory just to view the Purchase Orders

Summary:

We have a created a custom PO View Only role having View Purchase Orders privilege and created the user along with Manage Procurement Agent setup.

Initially Employee Role was assigned so user was able to see the POs for all BUs as per the data access given to the custom PO View Only role.

Recently we removed the Employee Role and user is unable to view any POs in the Manage Orders screen.

In fact, there is no supplier listed in the LOV while searching the POs with particular supplier.

What is the specific privilege apart from View Purchase Orders privilege is needed to view the POs without Employee role?