Not the point. Even human readers are going to be unsure about what is meant, that means automatic translators are always going to do even worse and mere chance

Not the point. Even human readers are going to be unsure about what is meant, that means automatic translators are always going to do even worse and mere chance becomes prevalent. If you look at how humans translate literature, the translator becomes a part of the work (in the new language) because translating it is an art, not a science. There is no 'correct' translation, only ones that deliver a human experience or interpretation of the original. So as I said, it's less useful as a test.