Their method extracts anything that binds specifically to androgen receptors and then applies conventional GC/MS analysis. Any peak that does not match known endogenous compounds (e.g. testosterone) is, by definition, a non-natural androgen-receptor-binding compound. You don't need to know its exact chemical structure to conclude that it shouldn't be there! Of course the way you defeat this test is to dope with a naturally occurring compound. But it should detect "designer" steroids of all kinds, both known and unknown, as well as SARMS. No?