Now, was that an airport policy or airline policy.
I flew FRA-SIN-SYD recently also and have heard and read of all these carry-on restriction on SQ. But they (SQ) had no problems with my regular two pieces (rollaboard and briefcase) at all three gateways. Maybe they didn't consider my briefcase/computerbag to be a counted piece.
The other known thing in my experience is that HKG airport is extremely strict. Airlines would issue special permit tags for business class/F passengers to permit that extra bag. Otherwise the agent at the security gate would send you back to the check-in area. And that is extremely effective!
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Cheers,
W