ADAs and ADOs use intelligence to decide their testing strategy.
In the case of Rupp, a whistleblower came forward and said to take a close look at NOP and their athletes. After 7 years of investigations and trial and appeal, with heightened scrutiny, no NOP athletes were ever sanctioned -- a result confirmed by USADA, WADA, an AAA Panel, and a CAS Panel. Ironically and tragically, the only NOP-connected "athlete" known to "dope" was the whisteblower himself, who was personally responsible for finding a WADA-legal method, both from a WADA "strict liability" point of view, and according to an explicit instruction memorialized in an email from Salazar. It is not clear if he was ever charged.
Makes me wonder if that was the best use of scarce anti-doping resources.