Hardcore winter snow/ice tires have a very soft compound with very flexible tread blocks. Under acceleration on dry surfaces the tires will literally "wind up" making the DSC thing they're slipping. In essence, they ARE, but it's the tire carcass in relation to the tread blocks, not the tread in relation to the road.
A simple anology, picture a huge draggster tire with tall, soft sidewalls. When a car launches the sidewall actually wrinkles because it has such a good grip on the track. It's essentially the same thing. The "performance" winter tires that BMW recommends don't have treadblocks that are as soft, so you won't see the same issues.
I personally would run similar tire pressures at all four corners with a soft snow/ice tire. They're not built for performance. They're built for gripping slick surfaces.