PJ2...
As always, a well written and very well thought out post.
As you suggest, some of the (many) lessons learned from AF447 were retrospective with respect to comparing the theories investigators had, versus what actually happened, and then delving into the resulting question: Can we (meaning investigators) use what we learned from AF447 in any valid way in analysing the known events of other so far "unsolved" accidents / disappearances; either to reinforce or to negate or weaken some aspects of a particular theory or postulation (ACARS messages being just one such source of information, albeit a potentially very valuable one).
Thanks also for your segue into logic and investigative procedures by referencing current events and the shadowy descending path so frighteningly evident in world affairs...