you must be joking if you consider 55 a "hard pace" especially for runners at this level.
To an elite runner most of whom can run a 47 sec 400 55 is like jogging. the main reason guys are running poor splits is to try and avoid trouble, a slower more even pace causes you to make many small accelerations to keep position. a 50 sec first lap keeps things a little more strung out.
You are also wrong about guys running 60-55, it used to be pretty common to negative split, you hang back to stay out of trouble. My biggest negative split was a 63-51, i had been sick and just could not get going, when i heard 63 at the bell i figured i would just run my tail off for the next 200 and drop out. But only about 100 meters in i had passed the whole field except for one guy so i backed off a little and kept going. I caught him in the last 50 meters but could not get around him. I would say in the late 60s and early 70s a good portion of runners ran in the sub 1:48 range running negative splits. In the late 40's i know that was the style and guys were running sub 1:50.