It seems odd that ride lengths do not show the additional distance that is the lead-in. You don’t have one place to view a rides detail including any lead-in distance. I have to view the ride I want to do in Zwift which shows if there is a lead in but not its length. Then I have to go to Zwift Insider to see the full ride details. Not exactly a great user experience and some of the lead ins can be 30 - 50% of the course distance so not an insignificant distance to have to factor in a ride for both distance and time. Zwift really need to sort this out as it doesn’t make for a cohesive view of rides and true distances in one app. User experience is now not good at all.
Lots of other posts on this. You should visit them and vote them up.