It may have been their intent to do a blinded IA in the summer, and having done the blinded data collection in Spring, or Summer 2015, that would have kept them... well... blinded.
And had they seen that all patients seemed to be eventing rather early, they may have suspected a problem. Especially since all patients also seemed to living longer.
In any event, they have very publicly stated may times they are still blinded.
So good point on your part, IMO.