Traction Control Off?
 

So my friend tells me he high centered his C7 S6 on a snow drift this morning. Says he couldn't move at all. Traction control was cutting engine power as expected.

He says he turned off the traction control and was able to drive away easily once he could rev the engine more without the traction control cutting the power.

Does this make any sense?

Yes, this makes perfect sense. Spinning wheels can help the wheels dig down through soft snow and find some traction.

It's in the manual and one of the reasons Audi provides a defeat switch of the ESC (track racing is another). One press of the button turns off ASR (not mentioned in the manual, if you press and hold the button for a few seconds, it also turns off the ESP - prob not a good idea in snow).

Normally, ASR will curtail the power to the wheel that's spinning to avoid loss of control when the car is pushed hard. When driving or stuck In deep snow though, the wheel will spin then stop - not a desirable effect under the circumstances. Defeating the ASR will no longer stop the wheel providing improved traction. Once you get rolling on a well plowed road, I've found it's best to turn the ASR back on.

Seems somewhat counter intuitive to turn your traction control off to get unstuck...

Does the C7 S6 use a Torsen center diff?

If so, that might explain it. As I understand it, a Torsen diff can only send a multiple of the torque at the slipping axle to the opposite axle.

No, the C7 chassis uses a Crown Gear center diff (same as in the RS5). It's Audi's Generation VI system and it apparently negates some of the limitations of the Torsen, which you mention, plus it reacts more quickly and is lighter.