Unusual?
Looking at the photos I suppose we can all agree that we can see bags trying to force their way out of the hole. It would appear that the trigger that caused the the damage was sufficient to rupture the internal containers to allow this to happen or the trigger for the damage came from the containers maybe more likely. If corrosion did create enough fatigue for decompression then I personally have doubts that the container would have damaged. Extremely lucky that all that rush of air did not cause primary structure failure ie floorbeams. Usually damage can increase significantly when other objects are dragged out with the high pressure air. Looks like the bags did everyone a favour by partialy blocking the hole and / or stemming the flow of air exiting the aircraft. If oxy bottles in the area might of been a slow leak plus + spark = bang. Investigation will probably resolve all speculation tho.