According to the PMBOKGuide, the project manager is responsible for managing the communication among stakeholders, and ensuring that the information needs of the project are met (Section 10.1). The project manager should also establish and enforce the ground rules for communication within the project team, and address any issues that may arise from unauthorized or inappropriate communication (Section 9.3.2.4). By pointing out to the project team and the customer that all information concerning the timeline of the project should be communicated by the project manager, the project manager can prevent confusion, misunderstanding, and conflict among the stakeholders, and maintain control over the project scope and schedule. This is also consistent with the Professional in Business Analysis (PMI-PBA)Examination Content Outline, which states that one of the tasks of a business analyst is to "communicate requirements information to stakeholders according to the communication plan" (Task 4.3). References:
* PMBOKGuide, 6th Edition, Section 10.1, Section 9.3.2.4
* Professional in Business Analysis (PMI-PBA)Examination Content Outline, Task 4.3

A benefits management plan is a document that describes how and when the benefits of the project will be delivered, and how they will be measured and evaluated. It also aligns the benefits with the organization's strategic objectives and shows how the project contributes to them. A benefits management plan can help the project manager communicate the value and benefits of the project to the stakeholders, especially if the project is in danger of failing or losing support. A benefits management plan is an output of the Identify Stakeholders process in the PMBOK Guide, and it is also covered in the PMI-PBA Exam Content Outline under Domain II: Needs Assessment. References:
PMBOK Guide, 7th edition, page 133
PMI-PBA Exam Content Outline, 2018, page 9

The benefits management plan is a document that describes how the benefits of the project will be delivered, measured, and sustained. It includes the benefits identification, analysis, planning, realization, and transition activities. By quantifying the expected tangible and intangible benefits in the benefits management plan for each phase, the business can increase the value of the project by demonstrating how the project contributes to the strategic objectives, customer satisfaction, and competitive advantage of the organization. Quantifying the benefits also helps to monitor and evaluate the performance of the project and the benefits realization process, and to identify and address any gaps or issues that may arise. Quantifying the benefits can also facilitate the communication and reporting of the value of the project to the stakeholders and the senior management. References: (Professional in Business Analysis Reference Materials source and documents) PMBOK Guide, 6th edition, Section 4.5.3.1, p. 123 PMI Professional in Business Analysis (PMI-PBA) Examination Content Outline, Domain IV: Traceability and Monitoring, Task 2, p. 13 Business Analysis for Practitioners: A Practice Guide, Section 5.3.1, p. 113