Wow, that text sure is full on cult.
The video Governing Buddy Jackson is theocratic warfare. It would be presumptuous of us, he says, but that's because he's speaking to a worldly court that is under the influence of Satan.
You can be sure that the conversation with a JW who questioned him on this would continue to establish the evidence from the Bible. WE don't claim to be God's only spokesman. God can use whomever he chooses ... He's even used Kings. He could make the stones cry out with His message. And then proceed to show why we are confident (as JW's) that GOD has appointed us His Witnesses. It would be presumptuous for us to make that claim, the claim is Jehovah's. ;)
You have to notice what they aren't saying when they are asked questions. It's spin while still feeling they are being truthful.
He didn't say "no" to the question.