GL Approval workflow fails for certain users

Summary:

We have a requirement to add a new GL approval rule, say Fin Rule ABC - along with the existing rules - which would use a new approval group (XYZ approval group of users X, Y and Z, all belonging to the same Department: PQR). The rule is defined in such a way that the approvals from any user belonging to PQR department must go to XYZ approval group, and any one of them (X or Y or Z) must approve it. Since X, Y and Z too belong to the same department, their approvals must also be routed to the