I would guess this has a lot to do with the radical design of the cam. In order for the bow to store that much energy and have a very strong force draw curve the design lends to have a lot of tension on the string at brace. Coupled with the fact that the string in located off center between the limb forks, you might expect to see this on any radical two cam bow. I've seen it on my old Proline New Wave Speed Stick. The cams were large and when drawn you could see the leverage they had over the axle. At mid draw the cams were very straight, I guess that is where the tension on the string and the buss cables were equalized. I think this might be what some are seeing on the Duallys.