You are picking apart the zero-sum part, I would also pick at the 'game' part. None of the examples are 'games'. They are just a few examples of conservation laws.

No decision making, no min-maxing actors etc.

Btw, when you have a single optimising actor, then moving along the efficiency barrier is also a set of trade-offs, which can be made constant-sum, if you set up your conversion factors just right; even if the optimisation itself is otherwise variable sum. (As a silly illustration: to produce more guns, you need to produce less butter.) But that observation doesn't really prove anything.