hey james,
you don't need to have tickets in your possession to list them on stubhub or ebay, so you can list them before they go on sale. these people are essentially saying that they will have them. check out the "delivery info" section - they're not promising the tickets until three days before the show.
scalpers list tickets that haven't gone on sale yet all the time. they prey on the insecurity of fans that they won't be able to get tix during presales/onsales. as an added bonus, it gives message boards a reason to think venue operators are colluding with scalpers.