The implication is clear: Jehovah is using them to communicate with the world. This is why it sounds so bad when they later claim to be fallible men who can get things wrong. If god wanted to use you as his channel of communication, why wouldn't he make sure that you got the message out clear and correct? Otherwise, doesn't it make god seem incompetent, that he cannot get his message across clearly? Why would your imperfect nature matter? Does god not know how to use people to get important messages across?
'God chose us to get this message to you, but please be aware that we might screw it up' is not the sort of thing that breeds confidence. It's the kind of thing a con man might say.