A shooting instructor who helped me with this same issue explained that L-R targets present visual problems for RH/right-eye dominant shooters because we are more likely to pick a L-R target up with our non-dominant left eye first. This can lead to the right not full capturing the target and then the left eye controls the "computer" more than normal. The result of a left eye controlled shot on a L-R target for a RH shooter is to shoot behind. I suspect that is perhaps why some shooters say they add more lead on the L-R targets, as this would compensate for the left eye making the barrels in the sight picture look like they are more in front of the target than they actually are.
While this works better on the range than in the field, I consciously turn my head a bit past where I expect the target to come from on a L-R shot. This gives my right eye a better chance to pick the target up first. It seems to work on clay range - and I just hope that is enough to retain it while in the field in the heat of the moment.
