In my readings, I have not seen anything to suggest that this was so and I would argue that it is more for cinematic reasons than historical reasons.

Artillery on the battlefield, especially during the Napoleonic era and afterward, was meant to push the enemy and create weak points by making the enemy morale weaken, so firing a volley all at once would have a larger effect of more shot hitting a line all at once. Second, artillery usually fired at the rate of the loaders, which varied between one and two shots a minute, easily giving the commanders time to change orders. Even more extreme when you get to the time of the Last Samurai when breach loading artillery starts to get more popular.

If the guns are all sighted for the same range, and that isn't correct, all the cannons will have wasted a shot. A series of shots allows for adjustment.