That's ridiculous. Proposing a nonsense solution certainly doesn't risk giving anything away. (You claim that there is a 100% likelihood the warden will cooperate and put the names in the boxes the prisoners request?)
If you think there's something wrong with the solution provided, why not just come out with it, and write "SPOILER WARNING" before it? I suspect you're misunderstanding something, though.
You're right, I misread it as "The prisoners get the Warden to label the boxes randomly", with the same implicit assumption as anigbrowl, that the prisoners don't have enough information beforehand to assign an order to the boxes.
