No, the New Covenant didn't change the need for God's word to be delivered with accuracy. And grace doesn't change the fact that someone's a false prophet if he speaks falsely in the name of the Lord or the need for us to cease to listen to false prophets.
Also, where's the repentance of the false prophets? I never see it. Would love to see it, but never have. Are the non-repentant still safe in grace?