I just got back from HKT to SFO via SIN yesterday at 7:30 AM. I slept for 8 hours in Coach in 48A on the A350 and did not have any jet lag. I stayed up till 10 PM last night with a 20 min nap and woke up today at 6:30 AM.
I had coffee yesterday and today. As of now I have no Jetlag. I took 2 Melatonin pills in the lounge 2 hours before my flight.