I believe perfect volleys were rare even by experienced troops. The sound of gun fire has been referred to as "the rattle of musketry". Parade ground evolutions in the field and under duress had to screw things up enormously.

In fact, as a former reinactor of the American War for Independence I can assure everyone that try as we might to fire nice, tight volleys, they were hard to pull off even with just 30 or 40 men firing. Despite using modern FF black powder that is mixed and corned to perfection (vastly better that 18th century powder) it was still very hydroscopic thus hang fires could delay ignition and cause the “rattling” effect. Despite having plenty of time to prepare meticulously before each show, once we marched off, flints still shattered and vents still clogged. Or all the men might not hear the fire order due to some great artillery discharge nearby. Not to mention the fact that being Mark I human beings, on occasion the men became inattentive or distracted (even without any real danger) and fired late.

Seeing the men march and fire imperfectly has been a great aspect of Total War since at least Rome. Desynchronizing these actions makes it all look realistic. If the troops have reverted to automatons then that is a bad thing IMO. Combat was very different from the Queen’s birthday parade at the palace.