1. Oracle Fusion Cloud Project Management
"Project Benefit Plans: Explained": "Benefit plans enable you to capture the anticipated financial and nonfinancial benefits of a project. You can create a benefit plan to support the business case for a project and to track the realization of benefits throughout the project life cycle." (This document directly states the purpose is to capture both financial and nonfinancial benefits to support the business case).
2. Oracle Fusion Cloud Project Management
"Implementing Project Financial Management and Grants Management"
Chapter: Project Foundation Configuration: Project Types: In the section describing the configuration of project types
enabling "Project Benefits" is listed as the step required to "create a benefit plan to capture the anticipated financial and nonfinancial benefits of a project." (This confirms the feature's role in planning for nonfinancial benefits).