Well in Romero's case, he didn't have a history of dominance in his minors career, with terrible control problems, and his 2011 was very much a case BABIP luck. Stroman has a history of dominance throughout his minors career with elite K/BB rates and great FIPs, the risk of it disappearing in his prime years in the majors is not particularly high.
Matt Moore, on the other hand, was a significant drop off from elite level potential, but that exception shouldn't deter a Stroman signing imo.