I do think they Prioritize ROW and then followed by EB1,EB2 and so on. Now hold your horses before you go about calling USCIS racist. In normal circumstances they prioritize ROW simply because it gives them an idea of the horizontal spillover to be applied to EB India and China as early as possible. Similarly they want to prioritize EB1 and so on, as they want to determine the vertical spillover across categories as soon as possible.