now visualize balance beam. the athlete performs the left cartwheel and finishes with her right foot forward and left foot back. this IS how a left cartwheel is performed. now if they were 'lefty' what would you have them do? they would either have to 'switch' their legs in the air before they landed the cartwheel or 'switch' their leg during the back walk over. both of these methods would be deficient because they take the body out of what it wants to do naturally. visualize this from the beginning of the left cartwheel and in to successive back walk overs without interuption. right leg kick over, left leg follow, right leg down, left leg down, right leg over, left leg follow, right leg down, left leg down and so forth. the body is in rhythmic coordination. right, left, right, left, right, etc; and the body will be in alignment when doing the back walk over from the cartwheel. switching legs causes anywhere during this sequential progression can cause misalignment of the feet and hips and poor hand placement.
So you teach every child in your program to do a back walkover on their opposite side? Honestly, I know very few people who do a back handspring back layout with a different lead split leg than their front leg for roundoff. A couple, but certainly not a lot. So while I agree that right cartwheel left back walkover "works" I'm still not sure what the point is here. The thing that makes the most sense is to use the best split leg (most flexible side). Also, I can do a left back walkover much easier than I can do a left roundoff. I've never had a pressing need to do either though.