To validate least functionality, the assessor must evaluate implementation (via security staff, admins, developers). Interviewing the policy author provides limited value since it does not confirm whether the policy is implemented in practice.
Extract:
"Assessors should confirm least functionality through interviews with individuals responsible for system configuration, security, and implementation. Policy documentation authors alone are not sufficient evidence." Thus, interviewing the policy writer is least useful.
Reference: CMMC Assessment Guide - Level 2, CM.L2-3.4.6.