Granted, they could still do a Final 3 even with 4 people in the Finale, like they did in China, but it means that they would have had to drop one of the immunity challenges and add an extra reward challenge so they would have a challenge to show for the first half of the Finale.
Well, if that was the case, they could probably take a challenge that they intended to be for immunity and just make it for reward. I don't think they'd have to drop or add anything.