According to the Great Circle Mapper, the distance SEA-KUL is 7017NM/12995KM whereas TLS-MEL is 9119NM/16888KM. I appreciate that neither of the flights were on a G/C track, but it gives a good indication of the distances involved.
1997 is a long time ago, perhaps Boeing has just "forgotten" to update the information?
Apart from Burt Rutan's Voyager, what is the longest non-refuelled flight ever?