Yes, what 559AS said. When Singapore did that route with the A340-600, I believe they used an all business class configuration so the passenger load was much less than a standard configuration A346. I was able to plan that route successfully in simbrief by dropping the passenger load down to 100ish. Also it's possible Singapore Airlines also has an exception or something, to use different enroute reserve fuel planning, which allows them to legally take less reserves for the enroute portion.