Again with the fin!
The report of the Working Group on Flight Data Recovery has a table of past underwater recovery operations (p. 12/13).
http://www.bea.aero/en/enquetes/flig...nal.report.pdf
For each of these accidents, it includes a column "tail floating?". (The reasoning being the proposal to place an additional set of flight recorders in the tail fin.) The table indicates "yes" only for AF447, a Kenya Airways A310 at Abidjan, and the A320 accidents at Bachrain, Sochi and Perpignan.
In all these four other accidents, the flight recorders were found, and the investigation showed that the cause of each accident had nothing to do with in-flight separation of the V/S.
In other words: Sometimes a cigar is just a cigar. And when a 'bus crashes at sea, the tail fin separates and floats. That's odd, but not a safety risk by itself.
And if the BEA report presents convincing evidence that the tail fin from AF447 separated on impact, too, there is no reason not to believe it.