Support gems / ascendancy that use flask charges

I'm using Concoct II and Ambrosia in my plasma blast, and it consumes the flask charges right when I click to charge up the attack, not when the shot fires. Idk if this is intended or what but trying to get the attack off and randomly getting stunned / accidentally dodge roll out, or when I think I've switch ammo and click 2-3 times to attack before realizing and it completely burns all the flask charges gaining no damage boost and can put me in a tight spot sometimes. Idk if it's possible or part of the vision to make them consumes flask charges when it actually shoots but I just wanted to mention it.