I certainly believe it is the electric power steering that is the major contributor to DW. While we never towed out 2004 Malibu Maxx, it had a similar oddity at low speeds - the steering wheel would do a mild DW in my hands while the engine was at near idle, and making sharp turns as one would do in a parking lot. It was disconcerting, but never enough that would cause a problem. If we had towed that car, we may have encountered DW!
Our 2012 Canyon has hydraulic power steering, BTW. I was surprised it still had the old hydraulic when we purchased it.