Law of physics:
-maximium friction (grip) is at about 15 % slip.
-at low speeds one needs a "delta" speed to get grip in snow.
Very good traction control systems =SAAB, has delta speed as a criterium - obviously BMW has not learned that lesson, hence the DTC.
Even with DTC, there is a stability control that is sufficient for most drivers/occasions.
If uncertain - don`t engage DTC.
The most fun you can have with your car is driving on an ice track - preferrably with studded tires
