You don’t learn how to pace on a treadmill
When running on a treadmill, it’s easy to “set it and forget it” and just lock into a target pace. Unfortunately, this method doesn’t teach you how to properly find and maintain pace on your own. As a consequence, you stunt the development of your internal effort and pacing instincts. On race day, when executing race splits is critical, you won’t have developed that fine sense of pacing that is crucial to running a negative split and finishing strong