The economics prize is listed on nobelprize.org ("the official website of the Nobel Prize") along with the other Nobel prizes, so I don't think you can justify calling it "unofficial".
Perhaps if the ACM renamed the Turing Award to "The Alfred Nobel Memorial Prize in Computer Science", the Nobel Foundation would let them get away with it.
Perhaps if the ACM renamed the Turing Award to "The Alfred Nobel Memorial Prize in Computer Science", the Nobel Foundation would let them get away with it.