The PMP exam is not a test of your knowledge of the PMBOK Guide. Instead, the PMP exam tests your general experience as a project manager as is described in the PMP Examination Content Outline.
www.project-management-prepcast.com/pmpoutline
You will find benefits realization as one of the cross-cutting skills in this document.
Training for Project Management Professional (PMP)®, PMI Agile Certified Practitioner (PMI-ACP)®, and Certified Associate in Project Management (CAPM)®