At the end in your example, I feel like I would have a deeper understanding of kimchi as it relates to Korean speakers, how “green onion kimchi” is different, and why that means someone is dead tired.

Then, next time it comes up I would understand it a little better due to slightly different context.

To me, that all feels like a win

Picture this situation in reverse. If you were instead a Korean person, digging in to why Americans associate cats and dogs with heavy rain? Or why English speakers eat butterflies before they do something on stage?

Learning idioms is useful and interesting, but I agree with the other commenter that you shouldn't look to an idiom to gain cultural insight.

“Raining cats and dogs” I had not looked up before, but I don’t hear it much currently so I would likely associate it with someone of a specific older age range, or someone younger who’s been around (or who is emulating) older people. Even that small inference brings some depth to understanding what someone is saying, and the character of the person saying it.

As for “butterflies in my stomach”, that’s even more important as it’s a tactile expression, describing the feeling of nerves as though there were literal butterflies fluttering lightly in one’s stomach. The fact that at some point an english speaker decided to express the internal feeling as though it was something tangible that other people around them were familiar with, that’s (imo) some pretty fascinating cultural context and something that I see repeated throughout english. I also suspect that it happens in many (but importantly not all) other languages/cultures, which is also pretty fascinating.