Well you have a point, and also its clear that D600 was created to make people of D90,D7000,D300s to move to FX so not to make D800/E suffer from the release of such camera it needs to be lower in spec's in many ways to leave room for D800 market grow as well as give juice for DX user to jump to FX user that can't afford a costly camera as D800/E upwards
It is all about product placement in different pricing tiers.