"not viable" is different from "impossible", it just means that it's gonna be too expensive and not worth doing compared to, yknow, just spending the money on renewables instead.

The article itself said it's still counting in future tech advances. Just because the alpha test is done at full size is different than being commercial scale imo. But we shouldn't even be judging power plants success on how well they can make profits, so whether it's commercial scale or not should not be relevant. Unfortunately it is, but the article gives no indication that it is commercially viable with current tech. Just that it physically exists.