Yes, for certain cases when both starting points are close to the pole and have opposite longitude lines, it may be shorter to cut through the pole instead of following the average latitude line. But for almost all cases, the current formula works. I didn't factor that scenario in because the vast majority of humanity doesn't live close enough to the poles for this to matter. The original usecase for this project was to find the midpoint between places of birth. Great catch though! I will make a note in the article clarifying this.