Centralized purchasing can simplify tasks and concentrate quantities. Its usefulness also depends on the ability to respond to local needs. An identical assortment can be convenient for the structure and inconsistent with some customers, especially when territorial differences affect demand.
At management level, I would distinguish a shared basis from specific needs. The criterion must be understandable and compatible with actual agreements. To discuss an exception, information is needed on the local demand and the consequences it produces for supply and management.
In a hypothetical example, some stores serve a clientele interested in small formats, while others encounter larger family purchases. The two needs can be read through sales and unmet requests, without automatically attributing the problem to the ability of the member.
The review should include availability, time and resources committed. The goal is to find a usable combination, with common advantages and motivated adaptations. Centralization gains value when it simplifies work and remains sensitive to the conditions that make the supply sellable at different points in the network.