Chicken and Egg which came first?
To answer the question: Yes the Korean War is a big part of the complex tale Random Thoughts it is a cycle of change after all—— and cycles are often complex things with multiple steps feedback onto the original change, it is not a singular thing.
When a story is complicated how you tell the story of what comes first is up for the author.
But the short of it is ... exactly Random Thoughts the Korean War changed South Korea's food culture.
I will explain why in a longer tedious post which I will try to make fun. But yes Random Thoughts the Korean War changed everything but it is only part of the tale.