OK,
I thought FIRM ticket holders who rebooked would have just been listed under the normal booking category for their class of travel.
I've looked at other flights, for example on Jan 1st and their are zero commercial standby's for any of the JFK, BOS or ORD flights. And I find that hard to believe that on all those full flight, there are no rebookings.
I'm not saying your answer is wrong, but it doesn't add up.
I;m still thinking it means repositioning crew or something along those lines. Does anyone have more info?