According to the 21.3 report, ~one hour after departure, oil quantity dropped to 1 quart and oil pressure was fluctuating (but still in acceptable range) - decision made to continue.
About an hour after that ATB due to unusual vibrations and possible oil smell in the cabin. Fire reportedly started after they deployed the reverser during landing roll.
So apparently they did not shut down the engine, and there is nothing in the report indicating they suspected they had a fuel leak.
Educated guess is the fuel/oil heat exchanger failed.