Board Thread:Naruto Discussions/@comment-33485854-20180606215933/@comment-1512913-20180610111353

Of course they were aware of the prosthetic arm while the databook was written. It just means that Naruto purposely wears the bandages on his prosthetic arm. An outsider might think his arm is wounded hence looking painful, but the reason behind the bandages is symbolic, not because of a wound.