This is how I see it changing the odds. You and a friend are both at the same table, early on in a tournament. You wake up with aces, raise, your friend reraises you, etc. You both end up all in, and you take the pot. You now have double chips, which early on in a tournament can enable you to be the chip bully and play more aggressively. Would your friend have gone all the way to showdown with his JJ if he didn't know that the worse he was going to lose was his time - after all, you're going to give him his buy-in back.
Let's say you bust him, take his chips, then pull out of your wallet some cash and hand it over to him in front of everyone. It's his buy-in back. How do you think the others at the table would feel? Especially if anyone else had gotten involved in the hand.
Having a prior agreement changes the odds because it changes what he can lose in that hand. Others at the table don't have that information. Even if it was just you and him in the hand, and nobody else folded out after the initial raise.
Now let's say you had JJ and your friend had AA, and you caught the river J and won the hand. Others in the hand wouldn't know that your play in this hand might not have been your standard line. Afterall, you have the opportunity to double up and really nothing to lose.
I wasn't implying soft play when I asked how this was not collusion. But soft play isn't the only form. It probably never occurred to you that anyone would find this situation unacceptable, but I'd be pretty upset if I found out that the person that just busted me had such a prior agreement with another player.
