Rod guy is fooling himself.
That racket is vertical. That is NOT a twist serve. A twist serve, the rackethead is accelerating upwards, and a vertical racket has already done that. Like a topspin forehand, look at the angle of the racket as it contacts the ball. It's almost vertical, yes, but still RISING as it contacts the ball. That is what gives the ball it's topspin, like a topspin forehand.