If you are 'God's sole channel of communication with mankind', you don't need to give it the old college try. You just speak, and it's true, and that's it. Truth isn't a baseball pitch that you take a swing at and sometimes you hit it, sometimes you don't. I doubt you'll find any Bible prophets trying to qualify their proclamations with legal-ese. But there's nothing vague about this statement. It's even attributed to Bible prophecy, same as saying it's God's own words. But they've been trained not to think in terms of 'true' and 'false' when it comes to their own beliefs. It's always 'prior understanding', 'past truths', etc. They can't look it in the eye or else it's a house of cards. Look at it from just the right angle, and for them, it's a solidly built house.
--sd-7