Do you believe statistics aren't real math? I'm not sure why the complaint. Sure it may be inaccurate, but as others said, along questions like: "do you have X heritage?" are already used as predictors for certain diseases. Genetic investigations just gets a little closer to the base truth, even if no one knows exactly which genes are doing which things.
But genetics may or may not be the "base truth" in regard to disease risk. It's difficult to tease out the effects of genes as opposed to environment. When your model has thousands or millions of genetic loci this only gets harder.
