I think there is a difference between a proof and the refutation of an argument. I expect proofs from scientific theories, and if a theory of consciousness would posit itself as scientific, I would be in perfect agreement with you that proofs or testable predictions should be provided. But I think here we are well into philosophy grounds, where neither proofs nor predictions are required. If that is the case, a philosophical claim needs to be actively rejected. I will admit that I still have to make my mind whether IIT is purely philosophy, purely scientific, or neither. Currently I don't think it's a theory of consciousness, rather just a model to "quantify" consciousness, without explaining its origin.

The author of TFA disagrees with you: "Most importantly, though, IIT is a scientific theory, unlike panpsychism."