LAST EDITED ON 05-04-14 AT 06:49 AM (EST)It doesn't matter what approach they end up using...it doesn't change the numbers or probability percentage.
Even if they didn't draw rocks and went the traditional route of whoever shouts out $500 first...Tony and one other from his alliance vs. Spencer only gives Spencer a 1/3 chance of shouting out first instead of 50/50. Tony and two other in his alliance vs. Spencer only gives Spencer a 1/4 chance of shouting out first. And so on.
As for the decision to draw rocks...my initial gut feeling why they changed it up and drew rocks this time might be because Tony opened up his big mouth during one of his gazillion confessionals and announced he would immediately use the tactic of being the first to shout out $500 to ensure him the advantage.
We all know Production doesn't like any player to be "one up" on them.