"Does that argument if factually valid have traction under Chinese law?" would normally have commas: "Does that argument, if factually valid, have traction under Chinese law?" to make more sense. Because of this, it can be rearranged, and a few words to make grammatical sense can be added to make "If this argument factually valid, does it have traction under Chinese law?" Essentially, it means the same thing, they only have a difference in tone [how you would say it], due to it's different structure. Native speakers, like me, would say the first question, because you are indicating the following sentence is a question (because of the "Does"), and therefore making people listen to you from the start. It also contains the criteria "If factually valid" WITHIN the question, so it is more interesting to listen to, and to say. When something is surrounded by commas in a sentence or question, it is known as an 'embedded clause', and is used by many writers and speakers to make their text/speech more interesting and involving. I hope this helps, and sorry if this long answer is confusing. I can shorten it if you request it.