At a glance, I don't see anything in there to explain why it would cause you to fail a substance abuse test?
I think because the tests don't necessarily detect a substance's presence, but detect abnormal levels of -test, estrogen, red cell counts, whatever- that is considered to be a sign of some kind of abuse. Otherwise, you'd never be able to detect blood doping, say, because you'd just find someone has X amount of red blood cells, everyone has them, so therefore, there is no evidence of an illegal substance.
So there is at least potentially an argument that an inflated level of whatever isn't always caused by taking some kind of performance enhancing drug or a masking agent.
Anyway, that's what I think the argument could be. I haven't been following this at all...