One interesting fact is that max RPM for an engine is not on Tale Off but during the climb. I wonder if it is relevant?
My understanding is that max RPM occurs in the latter stage of climb (ie above FL250). Where this event happened, the aircraft would have been about 4-6000 feet. The departures to the SE out of SIN of Runway 20C have a 4000 or above height restriction which is quite difficult for large widebody aircraft to achieve so it is probable that the maximum climb thrust would have been selected.
My mail says Eng#2 on that A/C has been carrying a Cat A Turbine Overspeed MEL since Tuesday.
This may have a bearing (no pun intended) on the investigation.