Hello, many contemporary university canteens are outsourced to private bosses, and many universities do not directly manage and operate canteens. The unified purchase of vegetables you mentioned is divided into the unified purchase of vegetables in all canteens of the school and the unified purchase of vegetables in all dishes in one canteen. Firstly, the former is analyzed. If a school has multiple canteens, one canteen is generally operated by one operator, and it is generally not purchased together. The latter depends on the size of the canteen. Sashido may buy his own food, and the canteen may ask the supplier to deliver it to his door. The supplier's delivery must be unified ordering and unified delivery, but Sashido does not necessarily purchase food in a unified way. It may be that he buys food wherever he sees it cheap, or that the boss and school leaders will buy a dish when they give the order.

I hope it helps you, thank you!