Wholly shit fanboi, you are a swallower. I applaud you for not wasting a drop.No it's not that complicated. But Eibach has like 3 spring kits. And ST has like 30+ spring kits for X3.
They are able to dial it in far more accurately for your car. We can have the exact same car but mine weighs 1700 and yours weights 2100 depending on accessories we have. Also where the weight is placed on the car like high mounted spare tires. And also your type of riding.
More options = more dialed in. Simple as that.
Nobody has done more testing on cars than ST. Period. Anyone here who thinks they know better with very little exception is sadly mistaken.