I don't have the slightest doubt that a classifier like zip code (or traditional observational disease markers) delivers much greater value than a genetic risk score model because its accuracy is nearly as good while its cost is a couple of orders of magnitude less.

I do have some doubts that the zip code actually gives BETTER prediction than the genetic risk score. I have difficulty believing that if someone had done a genetic profile on a patient and was willing to tell me either the patient's zip code OR the genetic risk score, that I would be better off asking for the zip code because it had greater predictive value. It' certainly not impossible (because of environmental factors that correlate with zip code), but it is surprising and I haven't yet seen actual research supporting it.