Jehovah's Witnesses: Are you certain you have the whole truth & nothing but the truth?

You are right and do make a good point! Yes it would be more appropriate to put it the way you said and they should "stop" using that phrase "the truth", because it falsely makes it sound like something that cannot fail. It also makes things sound like a phrase adopted from the Bible for a misleading purpose; in this case to make out like something it obviously is not