Kassadin Ult

So Kassadins ult is clearly a warp. He goes from point A to point B without traveling along line AB. Yet if there is a projectile along line AB Kass is hit by it. Why? It doesnt make sense. This same issue applies to other things such as flash or Tristana's rocket jump as well (although you could argue the character simply "aim up" in regard to Trist's ability)