specialized-
Well it says end of the attack not end of the animation. If you hit enemies with your projectiles you obviously didn't cancel the attack (otherwise where would the projectiles come from). This means that you did attack and the spells should trigger. If the current behaviour is what they want they should at least give an option to disable animation canceling, but again, i'm pretty sure its a bug.
The attack is what your character is doing. The projectiles are entirely unrelated except that they are created during the attack.
The attack is an animation on your character which starts, creates the projectiles, and then ends. The attack can end (and thus the spell trigger) before the projectiles hit anything, or afterwards - the attack ending has nothing at all to do with the projectiles. If you cancel the attack before it ends, it won't reach the end, and the trigger will not occur.