I'm saying that if zsh changed to keep its associative arrays in sorted order, and then you wrote a zsh program that relied on that behavior, you'd have a backward compatibility problem:
Ah! I was looking at that issue from the wrong end. Deep subject, backwards compatibility and my thoughts on it are naive but it seems to me sorta a tautology that new features require the new version and if your code uses the new feature then it won't work on the old version -- which is so obvious that I'm probably not really getting the problem ... mind, I understand that in shell culture using specific versions for specific things is not rare. But surely the user of a new feature must take care himself to make sure that his version is compatible? How could it be otherwise? Never mind, this is out of my experience.