I did not say "they wouldn't hold", I said that I did not see why they would apply, hence the working through that we have been doing.
If we start by considering the energy x in universe A, we can't very well arbitrarily include another distinct universe and its own energy as part of our system because we are effectively creating energy that was not part of our original system.
What I am saying is that from the point of view of A, if A is no longer connected to B, energy that ends up in B should be considered destroyed, and energy that arrives in A should be considered created.
If A and B are still connected then obviously they are one system (although they may be part of an open, infinitely repeating system as I mentioned earlier, which is a problem). But if they start and end in isolation, then one has effectively lost energy and one has gained it. An observer in either universe is not going to be able to distinguish destroyed/created energy from energy that has just been "reshuffled".
"Energy cannot be created or destroyed, it can only be changed from one form to another, which includes being mislaid in other universes".