From today's Tuna decision:
405. To us, it seems that the Panel's decision to exercise judicial economy rested upon the assumption that the obligations under Article 2.1 of the TBT Agreement and Articles I:1 and III:4 of the GATT 1994 are substantially the same. This assumption is, in our view, incorrect. In fact, as we have found above, the scope and content of these provisions is not the same. ...
Maybe Joost was right when he suggested that the Appellate Body was going to treat GATT III:4 differently from TBT 2.1. But I still have a hard time imagining that, in practice, detrimental impact will be enough for a violation of III:4.