Typhoid suggested that modern reverse systems only deflect the cold bypass air. I agree However the STOP actions will require the throttles being closed and then placed in the idle reverse position. This will ready the engine for a reverse power application if needed. I suspect a combustion chamber split on the inboard side of the engine causing a fire which was diverted into the fuselage by fortunately a low power steam of fan air. They were lucky, the 9 secs to stop the a/c plus a bit of thinking time before the fuel was cut off was enough to cause such major damage.