How to restrict the user to only manage and view his Purchase Requisitions

We are using new RSSP, and we notice that when granting the seeded roles to the user as (Procurement Requester, Advance Procurement Requester, Employee), and no custom role is associated. The privilege of:

- Managing and viewing other PRs are granted.
- Reassigning PRs to others.
- Update Preparer and Requester.
- Create a PR on behalf of others (selecting other requester on the lines).

Please advise, how these privileges are granted although only seeded roles are assigned as following screenshots:

Thank you in advance.