Excellent points
deSitter on composite structures.
Composite structures gradually bought their way on the airframe over the decades, and it's true, they don't deflect much before failure. Would like to know when they do the fatigue testing, whether they expose the sample to temperature and humidity cycles too. The pilots can answer here, but would assume an intercontinental plane spends its whole life on one line. Swampy England, high alt cold, hot Rio and back.
For 447 however, the photographic evidence of the vertical wouldn't necessarily support THAT structure failed below design load with margin. The empennage could have been peeled from the VS for instance. In the case where the horizontal failed downward, it would have dragged the two mounting points of the VS down with it in that area of dense supporting structure, explaining the rudder corner damage, since the VS would have rotated te down. The VS would have been only momentarily attached at the front after that. Or course this would have happened very rapidly.
Either way, VS first or HS first, would indicate an overload.