At the end of the day people were doing {**a, **b} or dict(d1.items() | d2.items()) (which is subtly different in that set order is arbitrary so which "wins" in

At the end of the day people were doing {**a, **b} or dict(d1.items() | d2.items()) (which is subtly different in that set order is arbitrary so which "wins" in the duplicate key case is arbitrary) in the wild, so I think supporting a natural dict-level union is the better option, even if it can't be all things to all people.