The difference is really the half-life of the drugs in question, as well as the specific performance effects of each. Also I am sure WADA would like proof of the reasoning behind the no fault decision, which is really something that would need strong evidence as back up. If they’re really going with the “Valieva accidentally took her grandfather’s medications on a day wherein she needed to perform well, at a time when she was recovering from a serious respiratory infection,” they need more than anecdotal evidence.