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.
Oil leak confirmed. That makes a lot more sense than a fuel leak (wing/pylon/internal to nacelle) detected in cabin air as there is no path to bleed air in flight. Engine oil, on the other hand, is right in the air path to bleeds via the compressor stage and fan bearing seals.
Thank you tdracer.
