You have missed the point. The point was that it is calculated by an algorithm (presumably a RNG), not by the user. Part of the game is that you thought you could affect the value by timing when you hit jump.
I never thought I could affect the timing. I assumed that it was just an animation.
I believe that was fixed in later Mario Party games: the animation was changed to move so quick that the player has no reason to assume they could affect the outcome.