I guess they have nothing to lose. In reality, lots of young designers would be smart to do the job for free, in order to gain attention. But if they do they are going to suck all the value out of golf design work pretty quickly, instead of cashing in on their success.
Also, to make such a bet, wouldn't the client have to give them a free hand to design as they pleased?
Betting on rankings is a slippery slope, ESPECIALLY if you do it publicly.