The "shorty" post were designed at a time where a typical correct fit often indicated a short post was enough. Also, the contact area of a Brroks Pro or similar to the saddle rails is much larger than say a Unicanitor. about 15-20 mm if memory serves on average. Go back to the 30's and bigger frames were the norm, the transition to a smaller frame and significantly lower handlebar position in relation to the seat on a road bike has been a long duration trend.

I ride with the tops of the bars about 100 mm below the saddle, this is not a current "race" position.