"I think it was done to confirm the synergy of RVX + rosuvastatin with the much larger BOM trial"

You are probably spot on Koo. I am just hesitant to assume 100% how the rosuvastatin subgroup analysis would be treated by the statistical analysis plan, by clinicians, cardio twitter, investor analysts, investors, bio writers, FDA/EMA, etc. in the event that the combined statin group is not also significant. This hesitance is primarily due to my own lack of knowledge in analysis of clinical trials, not any fault of anyone else. I am probably worrying about nothing. But I am not afraid to admit my limits of knowledge. It does seem like the trial was perfectly designed to confirm the synergy with rosuvastatin. 

BearDownAZ