There always needs to be a point of reference by which something can be termed stable and volatile. Here, it appears that point of reference is the SDR, where as the White Paper so states it is a Target Price based on the SDR. The Target Price is maintained by Target Rate Feedback Mechanism, which continuously modifies the incentives for borrowing and holding Dai (again from the white paper).
The SDR is a basket of currencies consisting of the U.S. dollar, euro, the Chinese renminbi, Japanese yen, and pound sterling , which is further modified by central banks and subject to further review and re-composition by the IMF.
If the point of reference for stability of the dai is a basket of currencies controlled by central banks, then it is a fallacy to say that this is a stable currency without central bank influence or intervention, because it is quite evident that the intent of the dai is to respond to such fluctuations in the SDR (effectively controlled by central banks and the IMF).
A new point of reference for stability needs to be discovered for the dai or you could just call it what is, an automated peg against a basket of fiat currencies.