Here is a snippet from Law 23, Part 4:
"vi) the striker is distracted by any noise or movement or in any other way while he is preparing to receive, or receiving a delivery. This shall apply whether the source of the distraction is within the game or outside it."
The conditions for a dead ball are quite clear. The batsman has to be distracted. If the batsman is not distracted, then the ball should not be declared dead.
The test is not "does the umpire think that the batsman should have been distracted." The test is "was the batsman distracted."
The timing is also interesting. When is the ball dead? A possible argument is that the ball should be declared dead immediately once an umpire feels that the batsman is likely to be distracted. However that's not the test. The test is if the batsman was distracted. The ball also does not have to be declared dead immediately once an incident has happened. See for example Tom Smith's description of how to rule on an injury:
The ball has been hit into the outfield and the fielder, in attempting to stop it, falls and is in obvious pain through a serious injury.
Before calling Dead ball, the umpire should look to see if the ball is continuing towards the boundary. If it is and it will reach the boundary almost immediately, he would not call Dead ball as once the ball crosses the boundary it is going to be dead anyway. By delaying the call he will neither be depriving the batting side of a boundary nor unnecessarily delaying getting attention to the stricken fielder"
(Smith, 2003, p.167)
It is completely within the consistent ruling of Law 23 to see what happens, and then call the ball as dead if necessary.
Which brings us to the Steven Finn breaking the wickets with his leg. The correct ruling here is that the umpire should see if the batsman was distracted or not before calling the ball dead.
If the batsman hits the ball for 4, or 2, then it should not be a dead ball, as the batsman was clearly not distracted. If the ball goes down the leg side for what would have normally been called a wide, then it should be called wide, not dead ball, as even if the batsman was distracted there was no opportunity for him to play a shot to it.
In the South Africa test where the precedent was set the first three were not called. It was only once Graeme Smith approached the umpire saying that he found it distracting that the umpire started to call it dead.
In the Super 8 match James Franklin did not make any such complaint, as as a result the law was applied incorrectly.
Incorrect interpretation of this rule cost New Zealand significantly in the last game. It would be crazy if it continued to be ruled incorrectly throughout the rest of the tournament. This is not something that the MCC Laws sub-committee needs to look at. The law is clear, and just needs to be applied correctly.