basically, it's using the fact that if you have selected lets say 15 abus guns and have them all in formation, if you now click far aawy , they start to get in a long line and travel like this. this is good for travelling long ways but for battle it's terrible.
so what should be done imo is before the battle starts, move in small steps (mass right click in front of them) so they spread out and can shoot all at once.
if you don't do this they have to first get in line and in position to shoot, if you keep the distance between your army and the place to right click, they'll just fire away directly which is what we want them to do.
this is nothing new but i feel few ppl pay close attention to it, and in the heat of the battle, simply forget about it
