There could be a reason for the apparent mistake. If the rear turn signals are actually front turn signals placed on the rear to allow for running lights, they would have to be criscrossed to keep the screws on the bottom. Do they have double filiment bulbs?
The Rattlebars site has a write-up on this mod.
When I did the run stop turn mod on my rear signals, I used front signals to do it. To keep the confusion to a minimum and prevent cross wiring, I stripped the sockets with wiring out of the signals and reversed them so the wiring colors matched up.