Castrol pays to have their name under the hood of the car, pays big money. Just like Mobil 1 pays big money to be under the Porsche "hood." The bottom line is if the rating is the same, it DOESN'T matter (API/SJ/CF,etc). Total makes an oil that is to BMW "M" specification, as does ENEOS. It's the "trap" that they pay for to get you in, that's why they pay so much money to put their name under the hood.
"! First rule of Italian driving, that which is in your mirror is not important !"