The authors provided indications of how the officers’ personal goals conflicted with personnel policies, but made no mention of what needs the military services presented that the officers were best suited to fill. This is a reality of any career, not just the military. You can have a great set of skills and experiences. But if your employer, or potential employer, does not need those skills or experiences, or if they find someone better suited, then you need to look elsewhere to have your individual needs met. That is not an indication of a broken personnel system. That is an indication of a personnel system functioning properly.
To prove that the cream of the officers leave service, one would need to 1) define what ‘best’ is, 2) measure current and departed officers against that standard, and 3) compare and analyze while controlling for all other relevant variables, which could include demographics, specialty and assignment history.