They get away with it by never admitting it happens yet dancing around the question of how big J guides their teachings. They are not inspired, the Watchtower is not inspired and yet if you deviate from their teachings one iota you can be disfellowshipped.
They really need someone to pin them down and say are you speaking for God or not? So how does god tell you what to say? But they'd be thrown out like Franz if they did that.