Yes, he had great game speed. Bill Walsh saw film of him in college and saw the same thing. With Montana at QB, they ran a lot of 20 to 30 yard posts, with Rice and Taylor taking them the distance. They rarely threw any long passes down the sidelines.
Speaking of sideline passes, I watched the first half of the Raiders game and EJ started. Right from the beginning he was decisive and fairly accurate on short passes, completing his first seven. He then attempted a bomb down the right sideline which, of course, was 5 yards out of bounds.