Mary is Joe's manager in the Role Hierarchy.

Even though Mary is Joe's manager in the Role Hierarchy, the lack of Read permission for the Invoice object on Mary’s profile prevents her from viewing Joe’s invoice records. Salesforce enforces object-level permissions, which override sharing rules, OWD settings, and role hierarchy. Without the Read permission on the Invoice object, Mary cannot access the records, even with Public Read-Only OWD or Role Hierarchy privileges.