
In many airports, including Changi, there is another (or the main) security check at each gate. Hence it is possible that passengers to UK and US (for the moment these are the only two countries) will not be allowed to bring any duty free purchases on board. This would severaly impact business at many airports.
I think the rule only applies to hand-carry luggage that passengers bring into the terminal. The duty free goods that they purchase will be after they clear security and should not be a problem.
If passengers are not able to carry anything apart from the bare essentials who will buy luxury goods from these shops at the
airport terminals.