In terms of marketing materials, it has been referred to as part of Main Cabin experience. However, I wouldn't assume they are necessarily following the convention here. It seems a bit pointless just to add a separate tie-breaker just for the small handful of domestic PS flights. It would be pretty straightfoward to do an experiment in the new year (with refundable fares) and see were people rank based on purchased MC, C+, fare classes, MM status, etc.