It did look like a pick to me as well, but someone here said in the rules it should be a pick when that is not true. In the rules it is a touchdown. a person cannot have "more" possession, you either have it or you dont. In this case I think they both had possession, jennings for sure caught the ball first but by the time they hit the ground tate had it as well. They both have possession so it is a touchdown. IF you dont think tate had it you are crazy, by the end of the scrum he was the one with the ball and he had the ball so tight once they hit the ground jennings couldnts roll away which is what he tried to do.