I guess he used the API from the app, add a large order and try to go to checkout. If McDonald want to avoid angry customers they alert that the item is out of

I guess he used the API from the app, add a large order and try to go to checkout. If McDonald want to avoid angry customers they alert that the item is out of stock, before finalizing the purchase. He then automatically do this for every store to check if the machine is working or not.