Neither. For the vaaaast majority of people, there would be no seizure and the odds of running into a random target that would have one is almost nill. Also if someone has that problem they simply can disable the graphics that allow you see the fireworks (I know I would and call it good).
So in order for it to be “metagaming” you would have to know a person’s personal medical issues enough, actively target them, and have them also not know enough to disable the fireworks or simply have the camera zoomed out to not see them. Seems like a waste of time to play a certain way in the hopes of winning via causing your enemy to seizure.