I'm not sure when EK placed their A340-500 order, but SQ ordered the -500 before the technical specs on the -200LR were finalized, and before they made their switch to the -200ER. At the time SQ made their decision, the -200X was lighter, shorter-ranged and only had @ 105k lb. engines, which made performance sub-par. Please note also that SQ has only ordered 5 -500s, which are intended to 'test the waters' of the ultra-long range market. SQ has publically stated they intend to determine whether these routes can be operated profitablly before fully commiting to them.
Honor the warriors, not the war.