That's entirely an implementation detail. The thing that matters for programmer experience is the specification of behavior: There's going to be an arbitrary order. You certainly can argue that you think it would be less surprising if trying this just failed, or that promising a stable order ties down implementations too much, but I don't think providing an order is that surprising.

None (as far as I remember) of the common "wat" examples about JS are interpreter implementation details, but specified behavior.

I'm mildly curious why CPython chooses to implement it this way, but if I had to guess: I'm assuming it is to provide a stable order between objects of different classes with the same hash() value. Hash-value being what I suspect is what the quoted answer misrepresents as "their address" (the address being in CPython the default fallback for objects that do not implement a hash() function), and being a good candidate to establish an arbitrary order.