To add a little context, it's the EU-mandated version of guaranteed origin labeling. There's also a French version, at least, and possibly some others as well. Usually, it's superseded by the local usage (DO, DOC, AOC, whatever), but when it's not, there's probably a reason. I can speculate what that reason might be in this particular instance, but it's only speculation, and someone who actually knows what COS intended might say otherwise. (I don't have a bottle at hand; does it eschew any and all Italian guaranteed-origin designations?)