Of course you wouldn't, because being Orwell, it's Orwellian by definition. But you could call another author's book Orwellian. Just as the quote in question

Of course you wouldn't, because being Orwell, it's Orwellian by definition. But you could call another author's book Orwellian. Just as the quote in question was probably referring to things that are Duchamp-like, as opposed to just Duchamp's.