I'll take a crack. We want folks to understand that they should use the measurement that causes the final course to be longer. Language is tricky on this point. I would usually say "use the shorter of the two measurements", but that assumes that you are measuring between two fixed points. Some folks, however, are working with the concept that they will start in the same place and end up in two different places. From their point of view "use the shorter" ends up as the wrong choice. The "Why" part of it is to help catch that mistake.
I would think the question can be answered by saying "#2, it shows the distance to be shorter so it ends up with a longer course." Or "I used the sum of the shorter measurements of each segment of the course". Or the like.
Does this question really serve to catch those mistakes, or not-- I do wonder if anyone has observations about that.