I can't speak for Korea, but the USA is almost unique in it's particular wiring practices. As such, one really has to "leave the USA behind" when leaving the borders.
The ampacity tables are, simply put, our best judgment call. One can always make a case for a higher, or lower, number. It's not at all surprising that different places have slight differences in opinion.
Code issues are not the only places where countries differ. Local construction methods, and lifestyle, have a great effect.
