Perhaps I can add a little information that will clear up the fuel situation.
First the credentials. I am a 744 Captain of 20,000 hours total flying time, and I have flown a 744 on 3 engines.
Second - the crew did the right thing.
OK.
Once we have reached the "tank to engine" stage of flight, at about 52 tonnes fuel remaining (ie 13 tonnes in each of main tanks 1-4, we normally feed each tank to its respective engine until landing (2 and 3 have an open crossfeed gallery, simply to keep that gallery pressurised).
On three engines, the dead engine's fuel tank will not feed any fuel in that circumstance, but we plainly want (need) to use fuel from that tank. To facilitate this, we use the override/jettison pumps in that tank to feed fuel to the remaining engines. They cut out at about 3 tonnes left in tank as they feed from the top of standpipes, intentionally leaving fuel that can only be reached by the lower pressure main tank boost pumps.
If you have not had experience of just how aggressive you need to be to feed this fuel to the other engines, it may catch you out later in the flight. In my opinion, it is best to decide how much fuel you wish to arrive with, in the dead engine's tank, and feed all other engines with this fuel early so as to allow normal tank to engine feed to the three live engines later in the flight (withing the constraints of lateral balance).
Here, the guys were left with more fuel in the dead tank than the others. However NONE OF THAT MEANS THAT THE FUEL WAS UNUSEABLE. If they had reached a state where fuel pumps in the low tanks were becoming uncovered, they would have operated with all pumps on, all crossfeed valves open, and, at that stage, all the fuel would have fed from wherever it was, to the three live engines. It just wouldn't have looked, or felt, very tidy.
Company policy requires the use of a Mayday call if you are going to land with less than reserve fuel (about 4.3 tonnes on a 744) and a PanPan if you think you MAY land in such a state. Now whether the guys on the day realised that that seemingly unuseable fuel was actually useable, I do not know, but nothing they did compromised the safely of the aircraft, or the passengers in the slightest.