The more the player "turns" the closer those projectiles will "bunch" together.
Ever played diablo 2? Slow missiles + Guided arrow.
you are thinking if a champion attacks VERY quickly, allowing them to apply burst damage in a set time in the future. now my question is, why would you want damage in the future as opposed to now?
the matter is simple. you are still attacking at the same amount of time spam (lets say twice).
long animation scenario (assuming they are moving towards you so that both shots "burst"):
_ _ _ 0 0 _
no animation scenario:
0 _ _ 0 _ _
notice that the killing blow occurs first in the no animation scenario. that's time longer for your opponent to react