I'm still baffled by the number of holes in the cheese having to line up for this to happen for the first time.
The farther back we take the the history of the aircraft, the easier it is to find a unique set of circumstances. So looking at the centre tank (a common feature linked to the two independent wing systems) it had a sub-zero cruise out followed by a sub-zero descent. These are the flight phases when atmospheric water enters the tank. Water scavenge does not work well below freezing, and I understand water warnings are occasionally reported when taxiing out after above-zero temperature fuel is loaded.
In this case the temperature at start-up for the return flight was below zero. If the fuel loaded was also below zero, there would be no water scavenge on take-off or climb out. The next opportunity for water to be scavenged from the centre tank would be aftert the descent to warmer levels, at which time it would be scavenged to the still cold wing tanks. Getting the holes to line up is not a problem - in fact it is a bit too easy, suggesting the holes are not big enough to bring an aircraft down.
For my money, the big question is how unusual is the history not just of that one flight, but of the history including the one before it and the conditions on the ground between the flights.
The cavitation damage statistics will be interesting. Any cavitation damage needs to be explained, because it is evidence of a fuel flow restriction at some stage of some flight. The fact that such damage is not unique to this aircraft might suggest that in this case there was just one hole too many, or the holes stayed lined up for just a few minutes too long.
The full explanation of the incident may well involve a long chain of coincidences involving more than one flight, and the investigation may take longer than usual as the correspondingly large number of alternative explanations are eliminated.
But there was no evidence of excess water in the fuel samples recovered ....
One value of different speculations about how an accident could have happened, is that it heightens awareness of how different accidents could happen.