Middle Marker - I think you will find that in the case of the JAL 747 the aircraft was pressurised and the cabin air then vented through the ruptured rear bulkhead in to the fin. As the fin was not vented it came apart. Subsequent modifications should now prevent this happening. In the case of this A300 I doubt it was sufficiently pressurised after only three minutes of flight to have a significant effect, apart from which, going by the photos', the fin is relatively undamaged. My opinion only.