I thought this was going to be about the detection of a giant ring system around an exoplanet, but it's merely in reference to diameter and mass. Maybe that's a particularly interesting size for an exoplanet but as far as I know it's not.
Maybe this is why we (presumably) haven't been detected ourselves.
So no, after that reset of expectations, I wouldn't expect Saturn's density to be widely known. Hell, I'm now starting to wonder if we've even reached the point that Saturn's rings might not even be associated with it at all?!?!