I don't think anyone here was implying some sort of government directive. More that there can absolutely be cultural/historic/economic ties between destinations that can affect passenger and crew dynamics, and that some airlines will differentiate their service depending on market (the 'manuals' discussed by the cabin manager in that interview).

Granted we did get a bit off-topic on the historical background from general service improvement, but that was also context on why on the IST-ICN route it is not uncommon to encounter some Turkish cabin crew members who speak better Korean than they do English.

But to give another example of a similar dynamic would be my Japanese friends who enjoy taking Taiwanese carriers when traveling to Taiwan from Japan. They usually pay a bit of a premium to take Japanese carriers when traveling to other Asian destinations, but with Taiwan they frequently encounter fluent Japanese speakers and generally better service due to historical and cultural ties there versus with most other Asian countries (although the reasons Japan has this relationship with Taiwan and why it contrasts quite a bit with most other Asian countries is rather quite different than the Korean/Turkish one... Which you will have to look up yourself if curious).