When you say the route is in 3 segments, do you mean that each segment is marked as its own activity? For instance, your mental image of the route is this is ONE thing, but on the Watch each segment is its own "Outdoor run" activity. If that's the case, my guess is that the Watch will recognize that as 3 separate things and if the middle segment (the one you are "running" or "racing") is far from your starting point when you begin your workout, it won't show up as a race route. At least, that's my guess.