it's been discussed here before.
YEs it is true that you can turn on DTC and even turn off DSC by holding the button down for 10 seconds. Use DTC only to maneuver out of a parking lot- driving around with DTC will cause tail spin and all the other spins and turns associated with winter driving- albeit to a degree. WIth DSC on, you can't even feel it when the car is skidding- it's solid on corners but with DTC you will feel the slips and slides along the way, so DO NOT drive with DTC on.
I'm not talking theory here, trust me on this I've done it
Even with DTC on, sometimes it snows so bad here in Canada that i can't quite get out from the parking lot- then i totally shut the DSC off and Xdrive my way out of there

That's the only time when I disable it.