All cubes in each round are scrambled the exact same way (a computer generates a 40-move scramble that is scrambled by volunteers before the cubes are returned to the tables).
Scrambles are not 40 moves, they're generally around 25 because they're somewhat optimized scrambles to reach a randomly generated state. Simply using a sufficiently long sequence of moves still provides some bias to certain cube states, which is why they don't do that.