They're no more about hiding mutable state than imperative languages are about hiding the purely-functional representation of state transfer semantics :) All y

They're no more about hiding mutable state than imperative languages are about hiding the purely-functional representation of state transfer semantics :) All you've done is listed alternative ways of implementing things, which is obviously possible in a range of paradigms (albeit with semantics that are usually harder to reason about in an imperative setting).