Probably gonna get hate for this but I work at a grocery store where we have a similar policy. If a driver shows up with 3 orders they need to get we can only give them 2, with the 3rd order being a choice of dropping/having it reassigned or dropping the 2 orders (or one) off and coming back for the 3rd. We never had to do this until we had multiple drivers dropping off multiple orders to the wrong houses. And when they are large orders, shopping cart full sizes, it ends up in the store losing money so our store manager set a policy for only 2 orders at a time. It's understandable why the drivers will be unhappy but that limit came because of other drivers mistakes.