Many middle-aged and older customers have a habit of mixing up leftover vegetables after a meal, and they encourage others to do so. The idea is that if everyone does the same, the restaurant can't reuse any dishes.
Meanwhile, honest restaurant owners want to assure customers that the their dishes are new. So they serve food in a way that will make it very obvious if it was reused. For example, kimchi is often served in long (~30cm) slices, so that customers will have to cut them themselves, as if breaking a seal.
Nice to learn that bit about long kimchi slices. I just assumed it was because people like it long, like with spaghetti.
So you're more likely to be served uncut kimchi in restaurants where the menu requires fresh crisp kimchi, as in bossam, kalguksu, and seolleongtang.