Cable sits too high above the chainstay to be mounted above the heart. IMO, should be below. I like the story above about the heart being an anti-slip point. Actually, I'd like to believe that, it would be a sure-fire way to accomplish multiple goals: 1) Not negatively impacting the frame steel or paint because it's over-torqued to prevent slippage, 2) avoiding slip damage to the paint/tubes if it were to rattle loose, 3) additional design aesthetic, 4) Remove questions about where to install the lower cable guide to get correct cable height/tension over parallel to the chainstay. There may be even more advantages, these are just the blatantly obvious ones (to me, at least)