ADC Attacks doing no damage on hit

I posted a question on twitter to Riot Games Support and they instructed me to make a bug post to be looked at/fixed

Currently from what I've been lead to believe if you cancel the attack animation before the missile fully leaves the champion nothing will happen damage wise and the missile will not travel any distance. However, I was lead to believe that if the animation continues far enough. that the missile will travel all the way to to target and hit, that it should do damage at that point. I have had quite a few games now especially on Vayne, that this is not the case. The animation will complete to the point of a missile leaving the champion and hitting the target (champion or minion) but do no damage. If the animation gets to that point shouldn't it do damage?