I've always thought that the importance of production and process methods for the analysis of WTO rules is greatly overstated, but I recognize that others find it relevant, or at least interesting. Hence, I feel obligated to point to the following statement by the AB in para. 5.63 of the Renewable Energy case in the context of GATT Article III:8(a):
What constitutes a competitive relationship between products may require consideration of inputs and processes of production used to produce the product.