It is changed indeed.

In the past:
PVG-SIN(stopover)-MEL-SIN(stopover)-PVG - allowed

Now
PVG-SIN(stopover)-MEL-SIN(stopover)-PVG - not allowed
PVG-SIN(Stopover)-MEL-SIN-PVG allowed
PVG-SIN-MEL-SIN(stopover)-PVG allowed

SG immigration could ask you for your printed itinrary and check your passport for recent SG VFTF stamps. If they think you are frequently using VTFT where your bona fide reason for entry is visit, they might decline you.