Limit = 55MPH, existing speed is between 45 and 70 = 25MPH max variance. Enforce limit, speed is now 45 to 55 = 10MPH max variance, a 60% reduction. Enforcing

Limit = 55MPH, existing speed is between 45 and 70 = 25MPH max variance. Enforce limit, speed is now 45 to 55 = 10MPH max variance, a 60% reduction. Enforcing limits will reduce variance. Please explain how this is flawed?