> Simply by declaring that objects are ordered, it becomes the case and it unlocks a whole lot of useful mechanisms.

I wonder what it allows that unordered objects with sorted keys if needed couldn't allow.

To me , it just adds an extra constraint on the programming language, but most of all, I don't like it because it's simply surprising. If the syntax look like a json object it should behave like a json object. Now if it was completely different syntax [a = b, c = d, ...] or something of that sort, or sexp ((a,b), (c,d),...).