Hi D.C.
To answer one question, no this is not a new WSOP rule, it's been a rule for a long time.
To add to Chet's comment further, the reason is as stated, it's not easy to be able to determine chip counts at all tables when the money is reached. In early tournament history, there was not even a hand-for-hand scenario. Play was just continued until a player was eliminated, with each table playing a different amount of hands. Thus, because of stalling, hand-for-hand was implemented.
More to your question though, the reason for chip counts being used if at one table vs multiple tables has some to do with hierarchy and some to do with organization and most to do with competitive opportunity.
First hierarchy / One Table Order - In order for Player A and Player B to go out in the same hand, there has to be another factor in the equation, Player C. In this equation Player C chips > Player B chips > Player A chips. That is for both Players A and B to be knocked out, Player C must have them both covered and win.
The logic is as follows in this all-in situation:
- If Player A wins the hand, he can not be knocked out and only Player B can be knocked out by Player C. Thus, if Player C beats Player B, you have one finisher in Player B.
- If Player B wins the hand, he can not be knocked out and only Player A can be knocked out by Player B. Thus, by Player B beating Player A, you have one finisher in Player A.
- If Player A wins the hand, and Player B's hand beats Player C's hand, no one is knocked out.
In all situations only Player A is at complete risk. Player A can be knocked out by Player B and by Player C. Therefore, because Player A is "covered" by all, they will finish lower should multiple players be knocked out. Even if Player A beat Player B's hand, the argument is mute for splitting equally because if not for Player C, Player A would still be playing and so would Player B.
Otherwise you'd have a situation where in a heads-up situation you only have one of two possible outcomes, A) Player A beats Player B and remains in the tournament or B) Player B beats Player A and a player is eliminated and placed in finishing order.
Organizational / Multiple Table Order - For multiple tables things become more complex. First you have to the task of knowing all players chips counts at all tables. The larger the tournament the more difficult the task. The task becomes even tougher the more players away from the money (or money change) that you are.
Ex#1 - Imagine you have 4 tables in action and pay 27. You have 28 players left. You are hand for hand. You have 1 player get knocked out at table #1. Easy enough.
Ex#2 - Imagine you have 4 tables in action and pay 27. You have 28 players left. You are hand for hand. You have 2 players get knocked out at table #1. Using the above rule, lowest chips is eliminated first. This is also easy to follow.
Ex#3 - Imagine you have 4 tables in action and pay 27. You have 28 players left. You are hand for hand. You have 2 players get knocked out at table #1 and 1 player get knocked out on table #2. Player A has lower chips than Player B at table #1. Player C is at table #2. Because Players A and B could not compete against nor eliminte Player C due to being at separate tables, so you have to treat them as equals. They split evenly.
Ex#4 - Imagine you have 4 tables in action and pay 27. You have 30 players left. You are NOT hand for hand. You have 4 players get knocked out at table #1. Using the one table rule, you place the player with the most chips in 27th place.
Ex#5 - Imagine you have 4 tables in action and pay 27. You have 30 players left. You are NOT hand for hand. You have 4 players get knocked out. One at table #1, two at table #2 and one at table #3. Again, Players A, B, C and D are all on separate tables and have no chance to compete against and eliminate each other. Thus, you have to treat them as equals. Moreover, when you're not hand-for-hand, chances are you are not paying close attention to chip stacks and neither are your dealers, as compared to other competitors.
Now expand those scenarios to paying 100+ players and even like in the case of the WSOP, paying 500+ players.
Lastly as noted in the organizational example, players must have the competitive opportunity to eliminate other players. Meaning you can't penalize a player for finishing at the exact same time as another player and place them lower in ranking based on chip count when that player never had an opportunity to compete against the player with more chips because of being at separate tables.