Not always true. For example the combat animation in the Arkham games - without it how do you test the combat is satisfying? Or the super cars in GTA, how to you test they break in interesting ways without having the finished mesh? Or the gun projectiles in Fallout - how do you tweak them to feel right without a good bullet mesh, physics, collision, particle effects and so on? Satisfying game play is just as visual as it is functional.