Hopefully its not going to be proven one way or another but I’m not convinced the South Koreans epically those less than 40 or so would not simply roll over after a strike on Seoul. It would be much easier for the North to pull off than a long range attack on the US...
There are plenty of communist sympathizers in the South. Their universities do a great job of indoctrinating them, much like ours.
Its possible some could roll over but I don’t think they’ll be given a choice. It’ll be fight or die.
Remember all the males have mandatory military service.