This has been common on all GM rear-wheel-drive vehicles since the early '70s. At issue is a non-adjustable alignment angle called "toe-out-on-turns". It refers to the diameter of circle each front wheel is trying to make. The two don't agree so one tire has to slide across the road to keep pace with the other one. With the larger cars of the '70s, it was very noticeable when you'd back up and turn that the front end seemed to be wobbling. That was from one tire sticking to the pavement and the stress caused the sidewalls to flex. Once the point was reached where it couldn't flex anymore, the tread skidded to catch up, then it started all over.
This toe-out-on-turns isn't really an issue, and there is no way to adjust it. It just has to do with the geometry of the front suspension and steering components. Mainly that is the steering arms that are cast as part of the spindles. Toe-out-on-turns is what makes the left wheel turn further than the right one when turning left so it makes a smaller diameter circle.
The engineers just got a little carried away. There was probably some other trade-off they were after.
Tuesday, March 17th, 2015 AT 6:27 PM