Re Singapore ATC.
One factor also contributing to the traffic flow into/out of Singapore is the totally unpredictable speed control of carriers based in the region - no names.
speed control was much more precise in Oz - 300 knots up and down, 250 below unless cleared. Any different and you requested it from atc.
In Sin, you will see 210 knots at 50 miles or 340 knots at 15 miles - depends on how comfortable the driver is on the day, or how scared he is, or how close to meal allowance the flight is, or how many clouds are in the sky.