The formulation used for that product has Porsche A40 approval (so has ran in Porsches approval test, which as you can imagine, is pretty severe), it also meets one of the most demanding specifications VW 505 01 which is for VW PD engines. Using oils without this spec can literally cause the cams to wear away due to the massive pressures due to the cam driven unit injectors. It's good stuff.
I use it in my S2000 on the track.
According to Castrol website only 5W-40 has A40 approval and the turbo diesel version does not list A40 approval.
Is it just a case they are both same oil and on the diesel branded version they don't list the Porsche approval as Porsche don't do diesel cars?