I would think that a batted ball that went all the way to the fence would have plenty enough momentum on it's own. So you would treat it as a "deflected ball", not one where the fielder added momentum to it. By the rule using the phrase "deflects off the defensive player" the assumption is that the ball did have sufficient momentum on it's own.
What if the fielder was swinging his arm....? Then we get to judge if the ball had sufficient momentum to go over on it's own, or if the fielder provided the momentum.
What if this was intentional? Then we high-five the fielder, because that would be a pretty neat trick!
If a fielder really could pull that off, and you really could judge it as intentional, then you could apply the rule for intentionally knocking the ball out of play. I think that rule would override 8-5-I.