The point is definitely true of all US-dollar commodities (which is basically every commodity price out there). I wrote the article, actually, in response to a question from a reader of our email who was confused when I wrote: "commodities are priced in US dollars, so their price goes down as the US dollar goes up." I had initially thought perhaps that this concept was, as you say, more obvious than it actually appears to be for many people.
Original article & question is here: http://beta.finimize.com/general/too-much-oil-copper-too-lit...