"carefully crafted" is probably a good description, much better than the initial report.
I agree, it sounds like they want to assure the rest of us, that it was something other than a inexplicable instantaneous combustion; rather - as you said - something external or structural, something unique that doesn't seem to endanger the rest of the fleet. They very much want to make sure to cover and exclude the engines, drivetrains, hydraulics and rotors.
It looks like they have a pretty good idea, but unlike us, can't speculate (
) until they have prove.
(one would think PHI has tried (and found) every flaw on that airframe - how many of all S-76 AD's are the result of an incident at PHI? 85%?)