Originally Posted by
Troopers
HKG-SIN-LAX requires backtracking. Valid SQ stopover cities are "on the way" to the destination from the origin.
It's not just the backtracking in the general sense. The award chart specifies that the 82k pricing between Zone 4 and the USA only applies to non-stop flights between those two zones, so SQ specifically intended that anything other than the non-stop HKG-SFO will be separately issued via SIN.