Whole-Part-Whole (WPW) learning is important in adragogy (adult learning) because, as Knowles states, previous experience and past learning are importantly integrated into present adult learning. This applies to the question of WPW learning because the first overview of the whole permits a connection between the present exposure to new knowledge and the learner's past knowledge.
The second phase of WPW, the parts of information, skill and activity, allows for perfecting the skill-base while drawing upon past skills and experience to gain proficiency and expertise in performance.
The third phase of the second exposure to the whole allows application of the "scaffolding" and the expertise developed from the whole-part phases to real-time and real life problems and requirements. Thus, WPW draws upon that which is unique to adult learning (as opposed to childhood learning), which is a reservoir of experience, knowledge and previous expertise.