Aside from the error of ignoring passenger capacity in reaching this conclusion, it also ignores range. The A380 has a range of about 9,700 miles. Both the A350-900 and B787-900 have ranges of about 7,500 miles. The fuel capacity has to be enough for the maximum range. When a longer-range aircraft has a higher fuel capacity, that does NOT mean it burns more fuel per mile. It would usually not load that much fuel for a short flight.