A manufacturing company has a long-standing practice of promoting its most productive assembly line workers to the role of shift supervisor. Recently, the company has seen a rise in employee grievances, a decrease in team efficiency, and high turnover among the newly promoted supervisors. From the perspective of a professional whose role is to cultivate and enhance leadership capabilities within an organization, critically evaluate the company's promotion strategy. What is the most significant flaw in this approach, and why does it lead to the observed negative outcomes?