I am very surprised Kathy. I have flown on RSSC air on American DFW to LAX everytime I go to Tahiti. I have always earned miles. The issue is that things are always different on every situation so you just cant really say it is "this for sure" or "that for sure" because it has been that way in the past.
I do have a lot of clients that always use RSSC and they get miles. Finally they get enough to get a free ticket. I think it is far more likely that you WILL get miles than that you wont. There can always be exceptions of course.
RSSC wont put your mileage number in the record for you so if you dont do that yourself then of course you wont earn miles. You are more savy than that though so I know you would have checked that out.