I believe very early MK6's had a sharkfin if the car had factory fit bluetooth. But in later cars (late 2010 onwards, maybe earlier), the bluetooth was revised and it no longer needed the sharkfin. I think the earlier Bluetooth system was rSap which doesn't work with iPhones.
If you see a sharkfin on a later MK6 then it's got Sat Nav from the factory.