It still might be good to have a way to win at Newcomb's, but on this view that thing will not be a decision theory.

Your comment captures the point well but I think this line is a little misleading. The proponent of CDT can say that a decision theory (held timelessly, including before the boxes were filled) might make you win at NP but they will say that decision theory is about making optimal decisions not about choosing optimal decision theories (though of course, the decision about which decision theory to follow is one possible decision and, the proponent of CDT will say, it is a decision that CDT handles correctly).