Looking at the pic they show, there is significant damage to the couplings. More than I have ever seen. And I have dealt with many sudden stoppage instances over the last 17yrs of component overhaul and repair.
I have alot of questions on what I see here, and find it hard to believe that bolts could have fallen out, although it is possible in a bad case of the swiss cheeze holes lining up.
I believe the engine was ripped from the airframe in this incident and gives pause to some of the damage seen as secondary. The reason I say that is because they show the aft driveshaft coupling torn apart, yet the tail rotor looks intact in the one picture. The liaison tube also bears significant secondary damage consistent with forced removal.
Like I said, there is alot of questions still, especially since the ASB came out to look at these bolts. Are they a cause, or is it secondary damage as well.