I was flying that night and had to divert and sit on the ground until after the end of the curfew period. I also heard the SQ aircraft inbound to SY (I think the ETA was around 5:30am), and he had been quoted a tailwind component of 27kts on 34L. Don't know what the max tailwind is for a 747, but I remember looking over to my right and seeing an equally puzzled face on the FO, when he continued his approach. All the other 747's (BA, QF etc) to my knowledge held until after 6am.
This tailwind was unforcast, and therefore the curfew in SY is a load of
under these curcumstances.... IMHO